Appeals to Khalil’s free speech rights are meritless. A green card is not synonymous with citizenship, though many seem to believe otherwise. Indeed, the federal government has the power to revoke a green card at any time, consistent with its statutory authority and assuming due process.

The Trump administration’s detention of a green-card holder who was a leader in the Columbia University protests against Israel has put a face on the debate over immigration and the limits of free speech, with a sympathetic twist: The man, Mahmoud Khalil, is married to an American, and they are expecting their first child next month.

If the Trump Administration comes out on the wrong side of this fight, it will be because defending free speech remains a politically lucid and powerful principle.