Should President Obama (and George H.W. Bush before him) have signed an unconstitutional law?

On Friday, President Obama signed into law S.2195, a unanimously-enacted bill designed to prevent Hamid Aboutalebi from entering the United States as U.N. ambassador from Iran. He also issued a signing statement announcing that he deemed the bill unenforceable…

Over at the Originalism Blog, Mike Ramsey criticizes the president’s decision to sign bill into law:

“The President should simply have vetoed the law. I don’t see how signing the law can be consistent with the President’s duty to uphold the Constitution (if the President is convinced the law is unconstitutional). (See Saikrishna Prakash: Why the President Must Veto Unconstitutional Laws). That seems particularly true when the unconstitutional provision is a standalone (as I believe it was here). It might be a different situation if Congress included an unconstitutional provision in a complex bill also containing many sections that the President believed to be constitutional and beneficial.” …