The US Department of Justice has asked a European court for permission to join Elon Musk's legal challenge to the European Union's fine against his social media platform X, according to a report by Quartz.

Musk's X Corp. is contesting a penalty imposed by the European Commission under the EU's Digital Services Act. The DOJ's bid to intervene signals direct US government involvement in a case that tests the reach of European content-moderation rules over an American company.

The intervention request, if granted, would place the US federal government alongside X in litigation before the EU courts, escalating a dispute that already carries significant diplomatic weight. The European Commission, which acts as the EU's executive regulator for major online platforms, issued the fine after finding that X breached obligations under the Digital Services Act.

For practitioners, the DOJ's move raises novel procedural questions. Interventions by non-EU sovereign governments in Luxembourg litigation are rare, and the request will require the court to weigh whether Washington has a sufficient legal interest in the outcome. Lawyers advising US technology clients operating in Europe will watch the procedural ruling closely, since a successful intervention could open a pathway for other foreign governments to support American companies facing EU regulatory enforcement.

The case forms part of a broader confrontation between Musk's businesses and European regulators. X's appeal and the DOJ's attempted involvement mark a significant step in transatlantic tensions over the enforcement of the Digital Services Act against US-headquartered platforms.

No date for the court's decision on the intervention request was reported, and the specific amount of the fine at issue was not stated in the available reporting.