President Obama announced the nomination on Thursday of a former government lawyer, who had been critical of the legal rationale for the Bush administration’s warrantless wiretapping program, to lead the Justice Department’s national security division.

The lawyer, David Kris, served as a senior Justice Department official in both the Clinton and Bush administrations from 2000 to 2003, and is widely respected in Washington for his knowledge of intelligence law. ... In late 2005, following the public disclosure of the N.S.A. wiretapping program approved by President Bush, Mr. Kris wrote a 23-page legal analysis that described as “weak’’ and likely unsupportable some of the Bush administration’s key legal arguments in justifying the program.

And when he was still at the Justice Department, he advised his boss, who was at the time Deputy Attorney General Larry Thompson, not to sign a mysterious batch of wiretapping warrants — which grew out of the program — because intelligence officials would not reveal how the information in the wiretaps was obtained.