Filed to the 9th Circuit Court of Appeals, which is expected to hear oral arguments on Tuesday, the brief argues that the travel ban is not constitutional and harms U.S. businesses.

Musk has drawn considerable criticism for agreeing to meet with the president to discuss various issues. The Verge even called him a “crony capitalist” for continuing to advise the president.

Musk had already come out opposing the temporary ban, which the Trump administration says will keep America safe from countries that harbor terrorists. The ban was blocked by a federal judge in Seattle on Saturday, and the Department of Homeland Security has stopped enforcing it for the time being.

But Musk also tweeted on Monday that “[m]any in America don’t realize how proud they should be of the legal system. Not perfect, but no where is the cause of justice better served.”

Other technology companies joining the brief on Monday afternoon include Adobe, HP, and Slack.

The original filing included the support of 97 technology companies including Apple, Airbnb, Google, Facebook and Intel.

The Department of Justice issued a response to the case, noting that the Constitution vests the federal government with “exclusive power over immigration.”

“The Executive Order is a lawful exercise of the President’s authority over the entry of aliens into the United States and the admission of refugees,” the Justice Department said in a response on Monday.

— Reuters contributed to this report