From the Associated Press:

..."We will submit legislation to the United States Senate which will...authorize the Congress to undertake judicial review of those signing statements with the view to having the president's acts declared unconstitutional," Judiciary Committee Chairman Arlen Specter, R-Pa., said on the Senate floor.

Specter's announcement came the same day that an American Bar Association task force concluded that by attaching conditions to legislation, the president has sidestepped his constitutional duty to either sign a bill, veto it, or take no action.

Bush has issued at least 750 signing statements during his presidency, reserving the right to revise, interpret or disregard laws on national security and constitutional grounds....

Seems to me that if Bush doesn't like a bill or thinks it's unconstitutional he should just veto it. This really seems to be an attempt to sidestep the seperation of powers.