The most relevant precedent is Section 301, the trade-law route the US Trade Representative has previously used to investigate digital-services taxes. USTR's own digital-tax materials describe past disputes in those terms: investigations, findings, proposed action and tariff threats. That architecture matters because it creates a record, identifies the countries and measures at issue, and gives the administration a procedure for turning grievance into trade action.
Section 301 is not a mere label. It is the mechanism through which USTR can investigate whether a foreign practice is unreasonable or discriminatory and burdens US commerce. In earlier digital-tax disputes, the United States used that framework to pressure countries whose taxes were seen as aimed at large American technology companies. That history gives Trump's threat a plausible route, but it also shows why the route cannot be skipped if the administration wants a durable tariff.
The route is narrower because the Supreme Court has already closed the broadest emergency-tariff path. In Learning Resources Inc. v. Trump, decided on 20 February 2026, the Court held that the International Emergency Economic Powers Act does not authorise the president to impose tariffs. The opinion undercuts any attempt to turn a sweeping digital-tax warning into a blanket border tax through emergency economic powers alone.
The politics of that route are uncomfortable for both sides. For Trump, procedure slows a message designed to sound immediate. For European governments, procedure gives Washington a formal record on which to build pressure. Each step creates more evidence for businesses, courts and trading partners to scrutinise.
As of drafting, the available Federal Register record did not show a new operative tariff proclamation tied to the reported threat. That absence does not make the threat empty. It does mean the next step is institutional: a USTR investigation, a notice, a presidential action under a statute that still supports tariffs, or some other legal instrument that names the target and the authority.