Donald T. Kinsella, 79, was appointed as U.S. attorney in the Northern District of New York in a private ceremony on Wednesday. But just hours later, Mr. Kinsella said, he received an email from a White House official telling him that he was being removed from the post. Reached by phone on Wednesday evening, Mr. Kinsella said that he did not yet know whether the White House email carried the force of law. He said he would discuss the matter with the district judges in the morning and go from there.