Two words: civil liberties, or the unitary executive. Here's a window into how he views these things, from a 1994 speech on crime (my emphasis):
"We look upon authority too often and focus over and over again, for 30 or 40 or 50 years, as if there is something wrong with authority. We see only the oppressive side of authority. Maybe it comes out of our history and our background. What we don't see is that freedom is not a concept in which people can do anything they want, be anything they can be. Freedom is about authority. Freedom is about the willingness of every single human being to cede to lawful authority a great deal of discretion about what you do."
Update (4/26): Rudy has long been overcompensating for his social views by way of his 9/11 credentials. This is cheap (even if smart) politics, and it's only getting worse. Here's another over-the-top quote from a speech the other day in New Hampshire:
"If one of them gets elected, it sounds to me like we're going on the defense," he said. "We've got a timetable for withdrawal from Iraq. We're going to wave the white flag there. We're going to try to cut back on the Patriot Act. We're going to cut back on electronic surveillance. We're going to cut back on interrogation. We're going to cut back, cut back, cut back, and we'll be back in our pre-September 11 mentality of being on defense."
Don't say you weren't warned.