I recommend Professor Steven Taylor’s review of the recent Congressional Research Service report on signing statements by US Presidents.
One thing Steven reports that the study reveals is that, while signing statements have been around a long time, the current president uses them in a manner that is qualitatively different from his predecessors. It is not signing statements, per se, that are troubling. It is the frequency with which they are invoked to challenge the very bill being signed.
For example, compare the four most recent presidents: GW Bush has used statements to claim constitutional objections in 86% of his 128 signing statements. The current president’s father, GHW Bush, made constitutional objections in 68% (of 214), Clinton in only 27% (of 391), and Reagan in 26% (of 276). A remarkable fact about these presidencies is that the current incumbent is the only one of these four who has had unified government (and not only majorities of his own party, but largely compliant ones) throughout most of his tenure, and has used this tool rather than the veto.
What is the big deal about a president claiming a bill is unconstitutional? The big deal is that if the president really believes that provision of a bill are unconstitutional, he has a right–no, a duty–to veto the bill. In our system, that means the entire bill. He has no constitutional right to sign the bill and then claim that parts of it are not binding on the executive branch, for any reason.
Under some (for instance, many Latin American) constitutions, presidents have this authority. Not in ours.
For previous dicusssions here about signing staments, please click on “Vetoes & Signing Statements,” above.