Microsoft Backs Anthropic in Pentagon Fight

Tech giant files amicus brief urging court to temporarily block Pentagon's designation of Anthropic as supply chain risk

Mar. 10, 2026 at 9:24pm

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Microsoft has filed an amicus brief in support of Anthropic's lawsuit against the Trump administration over the Pentagon's designation of Anthropic as a supply chain risk. Microsoft argues a pause in the designation is needed to avoid disrupting the U.S. military's use of Anthropic's AI technology and could have broad negative ramifications for the tech sector.

Why it matters

The Pentagon's designation of Anthropic as a supply chain risk would restrict federal agencies from using the company's AI products, which could significantly impact the U.S. military's access to advanced AI capabilities. Microsoft's support is a significant development that could bolster Anthropic's legal challenge.

The details

Anthropic first filed a complaint against the administration on Monday over the Pentagon's determination and President Trump's order for federal agencies to cease use of Anthropic's AI products. Microsoft argues a pause in the designation will help avoid 'disrupting' the military's ongoing uses of Anthropic's AI and warns U.S. warfighters could be 'hampered' if companies are forced to immediately alter their existing products and contract configurations with the Pentagon.

  • On Monday, Anthropic filed a complaint against the Trump administration over the Pentagon's designation.
  • On Tuesday, Microsoft filed an amicus brief urging the court to temporarily block the Pentagon's designation of Anthropic.

The players

Microsoft

A technology giant that has filed an amicus brief in support of Anthropic's legal challenge against the Trump administration over the Pentagon's designation of Anthropic as a supply chain risk.

Anthropic

An AI firm that filed a complaint against the Trump administration over the Pentagon's designation of Anthropic as a supply chain risk, which would restrict federal agencies from using the company's AI products.

Trump administration

The current U.S. presidential administration that designated Anthropic as a supply chain risk and ordered federal agencies to cease use of the company's AI products.

Pentagon

The U.S. Department of Defense that designated Anthropic as a supply chain risk, a move that Anthropic is challenging in court.

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What they’re saying

“The Department of War needs reliable access to the country's best technology. And everyone wants to ensure AI is not used for mass domestic surveillance or to start a war without human control. The government, the entire tech sector, and the American public need a path to achieve all these goals together.”

— Microsoft spokesperson

What’s next

A federal judge in northern California will take up Anthropic's request for a temporary block of the Pentagon's designation on Wednesday. Anthropic has also filed suit in the D.C. federal appeals court, requesting a review of the Pentagon's determination.

The takeaway

Microsoft's support for Anthropic's legal challenge highlights the broader implications of the Pentagon's designation, which could disrupt the U.S. military's access to advanced AI capabilities and have ripple effects across the tech industry. The case underscores the delicate balance between national security concerns and the development of transformative technologies.