Republicans Gaining a Backbone?

It has been reported that Senator Arlen Specter, a prominant Republican, is drafting legislation that would challenge the signing statements that has been often used by President Bush (story: http://abcnews.go.com/Politics/wireStory?id=2232349).
For the uninitiated, signing statements are a president's way of making comments on legislation, often showing what provisions they opposed or contain instructions on how the legislation would be carried out. These statements weren't used often by other administrations, but the Bush administration have used them hundreds of times, and used them as though they were law. This means that if Bush considered a provision illegal or relativly unimportant, the administration would ignore that provision entirely.

After five years of using this tactic, I'm not entirely sure if Republicans reject the use of signing statemtents in this way or just Bush's use of them. However, what this really signals is that Republicans are actually gaining a backbone, ready to take on the President. And this isn't something minor, this is something that has affected policy.
Let's hope that Republicans are ready to do even more.