A slew of America's biggest tech companies have swung behind Anthropic in its lawsuit against leaders in the Trump Administration.

Since Monday, Google, Amazon, Apple and Microsoft have publicly supported Anthropic's legal action to overturn Defense Secretary Pete Hegseth's unprecedented decision to label it a "supply chain risk".

In legal filings, the tech giants expressed concerns about the government's retaliation against Anthropic after it refused to let its tools be used in mass surveillance and autonomous weapons.

The government's behaviour could cause "broad negative ramifications for the entire technology sector", Microsoft warned.

Microsoft, which works extensively with the US government and the Department of Defense (DoD), said it agrees with Anthropic that AI tools "should not be used to conduct domestic mass surveillance or put the country in a position where autonomous machines could independently start a war".

A joint amicus filing, a filing by parties with a strong interest in a case, also came from several groups, including the Chamber of Progress. The tech advocacy group, funded by and representing Google, Apple, Amazon, Nvidia and many other tech companies, said they shared concerns over the government punishing Anthropic for public speech.

The Chamber of Progress stressed that it is "ideologically diverse" but concerned about the impact of the government's action on protections under the First Amendment of the US Constitution.

Facebook owner Meta is one holdout among major tech companies backing Anthropic's action. It left the Chamber of Progress in 2025 after years of membership.

The Chamber of Progress said its current members all "oppose governmental attempts to force or restrict access to speech".

Anthropic's lawsuit claims its free speech rights have been violated through government retaliation for its public statements, as Hegseth, President Donald Trump and others have accused the company of being "woke" or otherwise politically at odds with the administration.

The joint amicus brief called the department labelling Anthropic a risk "a potentially ruinous sanction" for businesses and little more than a "temper tantrum".

"If left in place, that sanction imposes a culture of coercion, complicity, and silence, in which the public understands that the government will use any means at its disposal to punish those who dare to disagree," the brief goes on.

Another amicus brief was filed by almost 40 OpenAI and Google employees.

And two dozen former high ranking US military officials filed their own brief, saying the government's actions "send the message that investing in national security carries the risk of capricious retaliation or disproportionate punishment for voicing disagreement".

Big Tech companies throwing support behind Anthropic may seem out of step, given that executives at the firms have supported and donated large sums of money to Trump since his return to office last year.

The suddenness and severity of the action against Anthropic appear to have crossed a line for major tech companies.

In a court hearing in San Francisco on Tuesday, a lawyer for Anthropic said the DoD had gone so far as to "affirmatively reach out to Anthropic customers, urging them to stop working with Anthropic".

A lawyer from the Department of Justice representing the government did not deny such actions and refused to say the government would take no further action against Anthropic.

"When the government starts to overreach and step on basic levers of capitalism, the alarm bells go off," Gary Ellis, the chief executive of Remesh AI who previously worked in US politics, told the BBC.

"If the government can do this and blacklist a company, one that has incredibly good technology, these executives know this is serious and can quickly impact them."

While officials have claimed they did not want to use Anthropic's technology for either mass surveillance or autonomous weapons, Anthropic claims Hegseth started to insist language in its government contracts specifying such prohibitions be removed.

Anthropic and the DoD spent weeks negotiating revised contract language, with the row spilling into the public domain in February. Anthropic chief executive Dario Amodei then went public with his refusal to entirely remove the guardrails.

It led to Trump berating the company and announcing on his Truth Social platform that Anthropic tools like Claude, in use by government and military agencies since 2024, would be removed from the entire government.

Hegseth then designated Anthropic a supply chain risk, branding it not secure enough for government use, the first time an American company has ever received such a label.

John Coleman, legislative counsel at Foundation for Individual Rights and Expression, a free speech advocacy group that was part of the joint amicus brief, said he expects more "clashes" like that between Anthropic and the DoD, given the tension between tech leaders being able to express themselves and government claims of national security issues.

"It's our hope that other Silicon Valley companies follow Anthropic's lead in staying true to their principles and rejecting federal pressure to abandon them", Coleman said. "A free society requires no less."