A judge said the excuse for arresting Mahmoud Khalil was unconstitutionally vague. Why isn't Khalil free?

Mahmoud Khalil , a legal permanent resident, could soon be released from custody thanks to a federal judge's preliminary injunction.

The ruling bars the government from "detaining" or "removing" Khalil "based on" Secretary of State Marco Rubio's determination that his pro-Palestinian activism poses a threat to U.S. foreign policy interests.

Farbiarz: Section 1227 was generally meant to be used, and has been used, for conduct outside the United States .

He says it's unclear how ordinary person would have notice that his conduct in U.S. may have impact on foreign relations with another country.

He asks: How will he know if people are hearing his words? that they are being influenced by them? Farbirz : Someone who "wishes to steer clear of the possibility of being removed from the U.K. will have to go quiet".

Federal judges have issued similar orders in other cases involving students whose criticism of the Israeli government was deemed contrary to U.S. foreign policy interests.

It remains unclear whether the Trump administration will comply with Farbiarz 's injunction by releasing Khalil or keep him in custody.

Trump is trying to punish people for constitutionally protected speech—and the Supreme Court has said that free speech protections extend to "aliens residing in this country".