Brightline rules promise clarity. The early enforcement record suggests something closer to friction.
Part I of this two-part series examined how mobile app-store anti-steering policies—rules that restrict developers from directing users to alternative offers or payment portals outside the app store—affect competition, consumers, and innovation. It also compared those policies with the restrictions upheld in Ohio v. American Express Co., in which the U.S. Supreme Court approved American Express’ anti-steering rules in a multisided credit-card transactions market.
Part II turns to enforcement. It compares how Apple’s App Store anti-steering policies and transaction fees have been treated in the Europe Union under the Digital Markets Act (DMA) and in the United States under federal and state antitrust law. The analysis focuses on what those divergent approaches have delivered so far for competition, commercial and legal certainty, enforcement costs, and the rule of law. Taken together, the early results raise serious questions about whether U.S. policymakers should continue pressing to import DMA-style ex ante regulation into American competition policy.
The DMA’s Promise of Clarity—Revisited
The DMA promises enforcers and private plaintiffs a simpler tool than traditional antitrust tests that weigh harms against benefits before labeling conduct unlawful. Article 5(4) adopts that brightline approach. It requires gatekeeper platforms, including app stores, to:
…allow business users, free of charge, to communicate and promote offers, including under different conditions, to end users acquired via its core platform service or through other channels, and to conclude contracts with those end users, regardless of whether, for that purpose, they use the core platform services of the gatekeeper.
DMA Recital 40 defines an “end user” as someone who “has already entered into a commercial relationship with the business user” and for whom the gatekeeper has been directly or indirectly remunerated for facilitating the initial acquisition. In practical terms, Apple may not block developers from communicating alternative offers or payment options to users, nor may it charge developers for making those communications. The DMA does still permit Apple to charge commissions for the App Store and iOS’s role in facilitating linked-out transactions—those completed outside the app store.
Despite this ostensibly clear framework, uncertainty has persisted more than two years after the DMA took effect.
When the DMA began applying to Apple in May 2023, Apple sought to comply with Article 5(4) by allowing developers to link to external websites for linked-out transactions. It paired those links with a caution notice advising users that Apple bore no responsibility for the transaction. Apple also imposed a 17% fee on consummated linked-out transactions, below the up-to-30% commission charged for transactions processed through Apple’s proprietary payment system, and somewhat higher than the 15% rate applicable to certain developers or transactions.
In April 2024, the European Commission opened a noncompliance investigation and soon issued preliminary findings. The Commission acknowledged that the DMA allows Apple to impose restrictions that are “necessary and proportionate” to protect iOS security and integrity. Even so, it concluded that Apple’s use of caution notices and its linking framework remained too restrictive and improperly limited developers’ ability to communicate free of charge, as Article 5(4) requires. The Commission also took the position that, although the DMA permits Apple to charge fees for facilitating linked-out transactions, the 17% fee was excessive.
Apple responded by further loosening communication restrictions and replacing the 17% fee with a 5% “initial acquisition fee” and a continuing 10% “store services fee.” Those changes did not resolve the dispute.
After months of additional meetings, the Commission fined Apple €500 million (approximately $588 million) for noncompliance in April 2025, rejecting Apple’s revised approach. Apple still lacks clarity about which conditions and fees the DMA permits. European authorities continue to consult stakeholders and observe market responses as Apple makes further adjustments, including reducing its external-transaction fees to as low as 5% for smaller developers. Even so, regulators maintain that any ongoing noncompliance remains Apple’s “sole responsibility,” exposing the company to the risk of additional fines.
That uncertainty is spilling over to the businesses the DMA aims to protect. The Coalition for App Fairness, a developer group that has long opposed Apple’s fees and restrictions, recently complained to the Commission that the prospect of further, still-undefined changes—including new policies that were expected in January—undermines their ability to plan investments and make ordinary business decisions. They note, with some irony, that U.S. antitrust courts have provided both developers and Apple with greater clarity about the platform’s legal obligations.
So what, by contrast, happened in the United States?
Injunctions and Evasion Under California’s UCL
In 2020, Fortnite developer Epic Games sued Apple in the U.S. District Court for the Northern District of California, alleging violations of Sections 1 and 2 of the Sherman Antitrust Act and California’s Unfair Competition Law (UCL). Epic challenged several App Store policies, including Apple’s requirement that developers process in-app transactions through Apple’s payment system at a 27% commission. Epic also argued that Apple’s anti-steering rules—which barred developers from communicating alternative purchasing options and payment portals outside the App Store—violated the UCL.
In a 2021 decision, Judge Yvonne Gonzalez Rogers ruled for Apple on all federal antitrust claims. The court held that Apple was a duopolist, not a monopolist, and that the challenged practices produced countervailing procompetitive benefits. The court reached a different conclusion under California law. It found that Apple’s anti-steering restrictions violated the UCL under the statute’s “tethering” and “balancing” tests, which apply a more flexible, and less demanding, rule-of-reason standard than the Sherman Act. The 9th U.S. Circuit Court of Appeals largely affirmed those findings.
The UCL allows plaintiffs to proceed either as competitors or as quasi-consumers. As a competitor, a plaintiff must show that the defendant’s conduct threatens an incipient antitrust violation, contravenes the spirit or policy of antitrust law by producing comparable effects, or otherwise significantly harms competition. Courts then weigh anticompetitive effects against procompetitive justifications, with both sides of the ledger “tethered” to evidence of harm to competition or to legislative policy. As a quasi-consumer, a plaintiff need not satisfy the tethering requirement and may instead proceed under a balancing test that weighs the utility of the challenged conduct against the gravity of the alleged harm.
Epic qualified under both theories. The courts treated Epic as a competitor to Apple in payment services and as a quasi-consumer of Apple’s app-distribution platform. Under both the tethering and balancing tests, the courts concluded that Apple’s anti-steering rules “‘threaten[ed] an incipient violation of an antitrust law’ by preventing informed choice among users of the iOS platform.”
The district court entered an injunction barring Apple from prohibiting developers from using buttons, links, or other calls to action to direct users to purchasing mechanisms outside the App Store. The 9th Circuit affirmed. Unlike monetary penalties, injunctions operate as equitable remedies and must be “no more burdensome to the defendant than necessary to provide complete relief to the plaintiffs.”
Apple responded by permitting linked-out transactions, while charging a 27% commission—3 percentage points below the 30% rate for in-app purchases processed through Apple’s payment system. Apple also allowed links to external purchasing sites, but imposed extensive design and placement restrictions. Developers could not use visible buttons; links had to conform to one of five prescribed templates; links could not identify users or enable automatic logins; and links could appear only once, on a single page, outside any in-app purchasing flow. As in Europe, Apple added a caution screen warning users that Apple bore no responsibility for the transaction and that Apple’s security and customer-service features would not apply.
Two months after the policy took effect in January 2024, Epic returned to court, arguing that Apple’s revised rules violated the injunction. In April 2025, the district court agreed, found Apple in civil contempt, and concluded that Apple had acted in bad faith by attempting to defeat the injunction’s spirit while maintaining technical compliance. The court barred Apple from charging any commission on linked-out transactions; limited caution screens to neutral disclosures that users were leaving the App Store; required Apple to remove restrictions on the style, language, placement, quantity, and formatting of external links; and permitted dynamic links that transmit user information to external sites, enabling automatic account logins.
Apple appealed. In December 2025, the 9th Circuit upheld the civil contempt finding but narrowed the injunction. The court held that Apple may restrict developers from placing external links or buttons in fonts, sizes, quantities, or locations more prominent than Apple’s own purchasing options. Preventing Apple from imposing such limits, the court reasoned, would elevate external links over Apple’s offerings and undermine, rather than promote, informed user choice.
The appeals court also rejected the district court’s blanket prohibition on commissions for linked-out transactions. It remanded the issue to determine what constitutes a reasonable, non-prohibitive fee. On remand, the district court must either replace the outright ban with a temporary sanction until Apple proposes a fee the court deems reasonable, or approve a commission tailored to Apple’s actual costs in facilitating transactions, including the use of Apple’s intellectual property. The 9th Circuit suggested that expert testimony from Apple and Epic, or a technical committee including representatives from Apple and the U.S. Justice Department (DOJ), could assist that analysis. Apple may also continue to enforce its generally applicable content standards for developers.
Evidence central to the contempt finding showed that Apple set its 3-percentage-point commission discount knowing that developers typically incur processing costs exceeding 3% when handling payments themselves. As a result, linked-out transactions remained more expensive for developers than in-app purchases processed by Apple. Internal Apple documents further revealed that the design and language of caution screens aimed to “scare” users away from external transactions, and that link-placement rules sought to make those transactions as difficult as possible. The courts also rejected Apple’s claim that its ongoing restrictions on communicating external links were justified by user privacy and security concerns, holding that such concerns cannot excuse noncompliance with conduct expressly required by an injunction. The 9th Circuit also observed that no developers had adopted linked-out transactions under Apple’s revised policy.
Even so, the appeals court emphasized limits on judicial intervention. It reaffirmed that Apple retains the right to charge a reasonable, non-prohibitive commission reflecting its role as a transaction facilitator. Apple’s contempt stemmed from setting a prohibitive fee that preserved the prelitigation status quo by rendering linked-out transactions economically unviable. That approach violated the injunction’s “implicit command to refrain from action designed to defeat” its purpose, even if it complied with the injunction’s literal terms. The 9th Circuit therefore curtailed what it viewed as an overbroad fee ban, while preserving Apple’s ability to recover legitimate costs.
Accountability Through Adjudication
The 9th U.S. Circuit Court of Appeals gave the district court a clearer roadmap for determining what fees Apple may lawfully charge. Its guidance specifies what payment structures and rates could satisfy the injunction, and what evidence Apple may submit to justify proposed changes. The revised injunction also draws firmer lines around how far Apple may go in restricting developers’ communications about external links and the accompanying caution screens.
The court affirmed the civil contempt finding, concluding that Apple failed to act in good faith when complying with the original injunction. It endorsed a broad—but temporary—fee prohibition as a sanction, limited to the period before Apple proposes an alternative policy that both complies with the injunction and preserves Apple’s legitimate interests as a platform operator. That approach penalizes Apple for contempt while creating strong incentives to propose a workable solution promptly. A proposal that falls short would prolong Apple’s inability to fully monetize its platform. At the same time, the court made clear that Apple faces no punitive fines so long as future compliance efforts proceed in good faith. In evaluating any revised policy, the court may rely on independent analysis, expert testimony, or a balanced technical committee.
This judicial approach contrasts sharply with the European Commission’s enforcement of the DMA. U.S. courts do not resolve compliance questions by polling market stakeholders—many of whom have vested interests in the outcome. Instead, the appeals process holds both defendants and decisionmakers accountable by requiring remedies to provide sufficient clarity about what the law demands. By vesting regulators with the final word, the DMA risks a less balanced and more discretionary system for policing similar vertical restraints. That structure heightens the danger of overbroad prohibitions that sweep in practices with context-dependent procompetitive or anticompetitive effects.
Judicial review provides the principal check on enforcement discretion. In the United States, Federal Trade Commission (FTC) decisions—including those from administrative proceedings and commission votes—are subject to review by federal courts and, ultimately, by the Supreme Court on questions of law. Courts apply antitrust principles to agency cases as they do to private suits. While courts afford agencies some deference—under Skidmore, giving agency interpretations persuasive weight based on expertise—that deference does not displace the judiciary’s duty to interpret the law independently and apply rule-of-reason analysis where appropriate. The same framework governs cases brought by the DOJ’s Antitrust Division.
The EU system operates differently. Commission determinations under the DMA—including gatekeeper designations and findings of noncompliance—may be appealed to the General Court and then to the European Court of Justice (ECJ) on points of law. Although EU courts conduct full judicial review of antitrust conclusions, brightline regulatory prohibitions narrow the scope of that review. Moreover, the Commission’s economic and policy assessments typically receive review only for “manifest error.” If the United States were to adopt DMA-style regulation, courts would likely infer congressional intent to grant administering agencies greater deference than under broadly drafted statutes such as the Sherman Act. Compounding the problem, Commission decisions—including fines—remain binding and can accumulate while appeals proceed, raising the cost of challenging potentially erroneous judgments.
As a result, regulated firms may face accountability for noncompliance or bad-faith compliance under both U.S. antitrust law and the DMA, while EU regulators themselves face fewer consequences for ambiguity or overreach. Apple’s experience in the EU illustrates the point: the company continues to incur penalties amid ongoing uncertainty about what anti-steering rules and fee structures the DMA permits. By contrast, in Epic Games v. Apple, the U.S. appellate court narrowed an overbroad injunction, clarified permissible conduct, and remanded unresolved issues for further analysis.
Institutional incentives help explain the divergence. Judges operate under meaningful accountability: their liability findings and remedies face appeal, creating incentives to tailor relief narrowly and articulate clear, specific obligations. That discipline reduces future disputes over compliance. Regulators, by contrast, may lack comparable incentives to resolve ambiguity and may instead leverage uncertainty, delay, and the prospect of mounting penalties to extract concessions unrelated to legal compliance.
Stakeholder consultation has an appropriate role when agencies craft new rules. For example, Section 18 of the FTC Act requires public input on proposed consumer-protection and trade-regulation rules. The rule of law suffers, though, when regulators consult interested parties to interpret binding rules while threatening retrospective penalties if good-faith compliance later proves insufficient.
Competition law can deliver equal or greater certainty than platform-specific rulemaking, while limiting arbitrariness and preserving experimentation. It allows firms to test potentially procompetitive practices, holds them accountable for anticompetitive conduct, and evaluates tradeoffs case by case. Market participants—including those the law aims to protect—benefit from fewer abrupt policy shifts than under ambiguous regimes that deter experimentation while obscuring what remains lawful.
Digital platform markets feature frequent innovation, short life cycles, and dynamic competition. Recognizing this, competition authorities in jurisdictions such as the United States and Taiwan have declined to adopt substantive, ex ante competition rulemaking for digital markets. Flexible adjudication offers a more adaptable framework. Existing statutes—including California’s Unfair Competition Law—already protect platform users as quasi-consumers while permitting context-sensitive analysis.
Allowing courts to tailor remedies narrowly—grounded in evidence and adversarial testing—reduces collateral harm to legal certainty and innovation. The Supreme Court has cautioned that case-by-case adjudication, rather than brightline rulemaking, suits contexts where agencies lack sufficient experience to “rigidify” tentative judgments into hard rules. The European Commission’s ongoing difficulty administering the DMA’s app-store anti-steering mandate underscores that warning, and suggests U.S. policymakers should hesitate before importing a costly regulatory model that has yet to deliver its promised clarity.
