Signing Statements and the Iraq Bill

Just a short musing here. The President has shown, through his as-yet untested use of signing statements, that he really doesn't care much about what the statutes say, so I wonder why he doesn't just sign the spending bill and announce that he's going to ignore it as some kind of unconstitutional infringement on Article II powers. If I were a more exciting version of Harry Reid than Harry Reid, I think that's what I'd dare the President to do. After all, Harry could say, no one's going to impeach the President for his repeated decisions, over the past seven years, to ignore Congress's laws through the use of signing statements, because the President has impeachment insurance. (Impeachment insurance comes in a package called "Dick Cheney").