Mahmoud Khalil has memorized the license plates of the vehicles that park on his block. He keeps an eye on reflective surfaces — storefront windows, car mirrors — that help him monitor his surroundings. When strangers walk behind him, he stops to let them pass.

A year ago, Mr. Khalil, a graduate of Columbia University and legal permanent resident, was detained and became the face of the White House’s crackdown on pro-Palestinian demonstrators. And more than 250 days after he was released by a judge, he is still living the life that the Trump administration imposed on him.

The government has accused Mr. Khalil, 31, of spreading antisemitism in the demonstrations that roiled the Columbia campus and, after he was already in detention, of failing to disclose pertinent information on his application for permanent residency. Mr. Khalil has said that criticism of Israel is not inherently antisemitic and that there was no failure of disclosure.

But the Trump administration has continued its efforts to deport him, leaving Mr. Khalil in a tense limbo, concerned that the courts might tip against him and that, even before that, the administration might arrest him once again, in violation of the law.

“The uncertainty really is like torture,” he said in a recent interview. He added: “I literally cannot plan anything. Whatsoever. A piece of furniture we cannot buy right now because we don’t know what’s going to happen.”

Immigration and Customs Enforcement did not respond to requests for comment on this article. The Justice Department referred to its filings in the case.