Lawyers for Mahmoud Khalil on Thursday said that they would seek testimony from Secretary of State Marco Rubio, who argues that though Mr. Khalil committed no crimes, his very presence in the United States enables antisemitism.

Mr. Khalil, a Columbia University graduate who led pro-Palestinian demonstrations on the campus last year, has been detained by the government for more than a month. He has a hearing in immigration court in Louisiana on Friday where, his lawyers acknowledged, it is…