Mahmoud Khalil, a Palestinian-born US permanent resident and activist, appeared Monday in the US Court of Appeals for the Third Circuit seeking to affirm a lower court’s ruling that blocked his deportation and authorized his release from detention.

His legal team from the American Civil Liberty Union (ACLU) argues that the United States Department of Homeland Security (DHS) and United States Immigration and Customs Enforcement (ICE) have engaged in retaliatory enforcement targeting his speech and advocacy related to Palestinian rights. Bobby Hodgson, assistant legal director at the New York Civil Liberties Union, an ACLU affiliate, stated: “The law is on our side: in the United States, ideas are not illegal, and government officials can’t weaponize a vague immigration law to incarcerate or remove people for expressing opinions with which they disagree.”

The federal government argues the district court erred, and its action was within the wide discretion of the executive branch for matters of immigration and foreign policy. It asserts that 8 U.S.C. § 1182(a)(3)(C) “delegates authority” to decide whether the physical presence of a non-citizen would have “serious adverse foreign policy consequences.” ACLU argues that the government’s argument in this matter and the provision itself are “unconstitutionally vague”, and its decision to punish “protected expression warrants the most stringent vagueness scrutiny.”

Khalil, a Columbia University graduate, was detained for a total of 104 days starting in March. The ACLU contends that Khalil missed the birth of his first child during the detention, and his eight-months pregnant wife was left alone due to the arrest. He was released after a federal court granted bail in June.