Microsoft and 22 retired generals back Anthropic's court fight against Pentagon

On March 11, 2026, Microsoft filed an amicus curiae brief in San Francisco federal court asking Judge Rita Lin to block the Pentagon's supply chain risk designation against Anthropic. Microsoft told the court that the designation forces government contractors to comply with vague and ill-defined directions that have never before been publicly wielded against a U.S. company. Microsoft said the use of a supply chain risk designation to address a contract dispute may bring severe economic effects that are not in the public interest. The filing asked the court to issue a temporary restraining order blocking the designation to allow for more reasoned discussion. Microsoft also formally endorsed Anthropic's two ethical red lines: that AI should not be used for domestic mass surveillance, and that humans should remain in the loop for high-stakes automated decisions. Sherwood News Federal News Network

A separate amicus brief was filed on the same day by a group of 22 retired senior U.S. military officials, including former CIA Director Michael Hayden and retired Coast Guard Admiral Thad Allen, who led the federal government's response to Hurricane Katrina. Their brief explicitly set aside the substance of the Anthropic-Pentagon dispute and focused on what the group characterized as a fundamental abuse of government authority. Something more basic is at stake: the misuse of powerful national security authorities by civilian political leadership, not to address the serious concerns that led Congress to delegate the authority in question, but as retribution against a private company that has displeased the leadership. Far from protecting U.S. national security, the Secretary's conduct here threatens the rule-of-law principles that have long strengthened our military. Stars and Stripes Military.com

Earlier supporting briefs had been filed by AI developers at Google and OpenAI. A fourth amicus brief came from the Cato Institute and the Electronic Frontier Foundation. The spectrum of organizations — ranging from the Cato Institute on the right to EFF on the left, and from Microsoft as a corporate interest to retired military leaders as national security veterans — illustrated the breadth of opposition to the Pentagon's legal theory. The case is before Judge Rita Lin in San Francisco, with a hearing scheduled for March 24, 2026. The Hill CNBC

The backstory of the dispute runs through Anthropic's $200 million Pentagon contract negotiated under the Biden administration. That contract allowed Claude to be deployed across classified military networks but included two restrictions: Claude could not be used for mass surveillance of American citizens, and it could not be used to control fully autonomous weapons without meaningful human oversight. The rupture began in late January 2026 when Anthropic started pressing the Pentagon for details about how Claude had been used during the U.S. military operation that led to the capture of Venezuelan President Nicolás Maduro. The DOD insisted Anthropic must allow all lawful uses without restrictions. Anthropic CEO Dario Amodei said the company cannot in good conscience accept that condition. Sherwood News

The retired military officers' brief carries particular weight because it directly contests the Pentagon's framing that the Anthropic dispute is a national security matter. The officers argue it is the opposite — that abusing national security authorities to coerce a private company's product policies is itself a threat to the rule of law that the military exists to defend. The list of signatories includes Admiral C. Steve Abbot, Admiral Thad W. Allen, and Vice Admiral Donald C. Arthur, among 19 others. Stars and Stripes

Microsoft's brief also raised an operational concern: removing Anthropic's Claude from military systems while Operation Epic Fury is underway could hamper U.S. warfighters at a critical point in time. This argument created a paradox for the Pentagon — it is simultaneously using Anthropic's AI in active combat operations against Iran while designating Anthropic as a supply chain risk. Federal News Network

The case before Judge Lin represents a significant test of how far executive branch national security authority can extend into the commercial regulation of private AI companies. Legal analysts across the political spectrum have noted the legal theory is weak because Congress delegated supply chain authority for adversarial national security threats, not contract disagreements. OpenAI CEO Sam Altman issued a memo to staff saying OpenAI shares Anthropic's red lines on mass surveillance and autonomous weapons, while simultaneously negotiating with the Pentagon over guardrail terms. On March 26, Judge Lin blocked the Pentagon designation. CNN