Artificial intelligence startup Legion LegalTech has sued the US government over an order that forced Anthropic to block foreign nationals from accessing its most advanced models.

The company filed the lawsuit Tuesday in federal court in Washington, challenging a June 12 directive issued by the Commerce Department’s Bureau of Industry and Security.

The order required Anthropic to suspend access to Fable 5 and Mythos 5 for any foreign national, including people working inside the United States.

Anthropic disabled the models for all customers worldwide on the same day because it could not guarantee compliance while continuing to offer broader access.

Legion is based in the United States but employs Canadian software developers working from Canada. The company uses Anthropic models to build drafting and case management tools for attorneys.

Legion said the shutdown immediately removed the latest model at the center of its development work and sidelined members of its engineering team.

The company described the damage as immediate, irreparable and potentially existential, arguing that lost ground in the fast moving AI industry cannot easily be recovered.

Legion is asking the court to overturn the government directive and plans to seek a preliminary order blocking its enforcement while the case proceeds.

The lawsuit names Commerce Secretary Howard Lutnick and other government officials as defendants. Anthropic is not a party to the case.

The Commerce Department and White House did not immediately comment on the filing.

Anthropic said it remains grateful to the administration for working toward a resolution and remains committed to protecting critical infrastructure and maintaining US leadership in artificial intelligence.

The government issued the restrictions after raising national security concerns about the potential use of Fable 5 and Mythos 5 by foreign military or intelligence organizations.

Anthropic has said the directive did not provide specific details about the alleged threat. The company believes the government acted after reviewing a technique that bypassed some Fable 5 safeguards and identified a small number of previously known software vulnerabilities.

Anthropic argued that similar capabilities are already available through other public AI models and said the reported bypass did not justify removing the models from all customers.

The dispute adds to broader legal tensions between Anthropic and the Trump administration. Anthropic has separately challenged the government’s decision to place the company on a supply chain blacklist following disagreements over military uses of its technology.