NEW YORK (CNNMoney) -- Elon Musk has signed on to fight President Trump's travel ban.

Tesla, SpaceX and 29 other companies joined dozens of other tech companies Monday in the legal fight, declaring that Trump's executive order on immigration "violates the immigration laws and the Constitution."

That brings the total number of companies who've cosigned the friend of the court brief to 127.

Musk's companies, Tesla and SpaceX, were not among the original list of nearly 100 companies that were part of a court motion on Sunday evening.

Other companies that joined the brief Monday include mattress startup Casper, on-demand janitorial startup Managed by Q, and the messaging startup Slack.

The motion was filed with the Ninth Circuit Court of Appeals, which on Sunday morning denied the U.S. government's emergency request to resume Trump's travel ban. The appeals court has asked for both sides to file legal briefs before it makes a final decision.

Musk, who is the CEO of both Tesla and SpaceX, was one of about a dozen top tech execs who had met with Trump in December. Executives from Palantir, Cisco, Oracle, and IBM also attended the meeting. They have not joined the friend of the court brief.

The big four telecom companies, AT&T, Verizon, T-Mobile and Sprint, have not joined the brief.

Elon Musk is also a member Trump's Economic Advisory Council. The group met last Friday and Musk later tweeted that, at his request, the travel ban was "first and foremost" on the agenda.

Musk publicly criticized the travel ban in one tweet as "not the best way to address the country's challenges."

SpaceX, as well as Oracle and Palantir, all have lucrative government contracts.

--CNNTech's Seth Fiegerman contributed reporting

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