A clear violation of his First Amendment rights:

Facing a deadline from an immigration judge to turn over evidence for its attempted deportation of Columbia University activist Mahmoud Khalil, the federal government has instead submitted a brief memo, signed by Secretary of State Marco Rubio, citing the Trump administration’s authority to expel noncitizens whose presence in the country damages U.S. foreign policy interests.

…

Rather, Rubio wrote Khalil could be expelled for his beliefs.

He said that while Khalil’s activities were “otherwise lawful,” letting him remain in the country would undermine “U.S. policy to combat anti-Semitism around the world and in the United States, in addition to efforts to protect Jewish students from harassment and violence in the United States.”

Pressed for evidence against Mahmoud Khalil, government cites its power to deport people for beliefs

The U.S. government has submitted a two-page memo from Secretary of State Marco Rubio as its main evidence in its deportation case against Columbia University activist Mahmoud Khalil.

https://apnews.com/article/mahmoud-khalil-columbia-university-trump-c60738368171289ae43177660def8d34