Your new book, “Crisis and Command,” is an eloquent, fact-laden history of audacious power grabs by American presidents going back to George Washington. Which president would you say most violated laws enacted by Congress?

I would say Lincoln. He sent the Army into offensive operations to try to stop the South from seceding. He didn’t call Congress into special session until July 4, 1861, well after this had all happened. He basically acted on his own for three months.

Are you implicitly comparing the Civil War with the war in Iraq, in order to justify President Bush’s expansion of executive power?

The idea is that the president’s power grows and changes based on circumstances, and that’s what the framers of the Constitution wanted. They wanted it to exist so the president could react to crises immediately.

Do you regret writing the so-called torture memos, which claimed that President Bush was legally entitled to ignore laws prohibiting torture?

No, I had to write them. It was my job. As a lawyer, I had a client. The client needed a legal question answered.

When you say you had “a client,” do you mean President Bush?

Yes, I mean the president, but also the U.S. government as a whole.