Microsoft has made its most significant legal statement on AI ethics to date by filing a court brief in support of Anthropic’s challenge to the Pentagon’s supply-chain risk designation, putting the company’s enormous credibility and resources behind the principle that technology companies have a right to set ethical limits on how their AI is used. The brief was filed in a San Francisco federal court and called for a temporary restraining order. Amazon, Google, Apple, and OpenAI have also backed Anthropic through a separate joint filing.
The dispute began when Anthropic refused to allow its Claude AI to be deployed for mass surveillance of US citizens or to power autonomous lethal weapons as part of a $200 million military contract. Defense Secretary Pete Hegseth labeled the company a supply-chain risk, triggering the cancellation of Anthropic’s government contracts. Anthropic filed two simultaneous lawsuits in California and Washington DC, arguing the designation was unconstitutional and unprecedented for a US company.
Microsoft’s filing carries particular significance given its status as one of the Pentagon’s most deeply embedded technology partners. The company integrates Anthropic’s AI into military systems and is a partner in the $9 billion Joint Warfighting Cloud Capability contract. Microsoft publicly argued that the government and industry must cooperate to ensure advanced AI serves national security without crossing ethical lines related to surveillance or autonomous warfare.
Anthropic’s court filings argued that the supply-chain risk designation was an unconstitutional act of retaliation for the company’s publicly stated AI safety positions. The company disclosed that it does not currently believe Claude is safe or reliable enough for lethal autonomous operations, which it said was the genuine basis for its contract demands. The Pentagon’s technology chief publicly stated that there was no chance of renegotiation.
Congressional Democrats have separately asked the Pentagon whether AI was involved in a strike in Iran that reportedly killed over 175 civilians at a school, raising questions about AI targeting tools and human oversight. These legislative inquiries are adding urgency to an already extraordinary legal confrontation. Together, Microsoft’s significant legal statement, the industry coalition, and congressional pressure are creating a defining moment for AI governance in American national security.