Obama apparently left Washington without signing the bill and then ordered that the bill be signed by "autopen."
A blog post by legal scholar Eugene Voloch, a blogger and professor at UCLA, points out that such electronic or proxy signatures have traditionally only been valid when the person ordering the signature has actually been present. Obama was not and therefore the signature is arguably not valid (although a 2011 White House legal opinion concludes that they are).
Voloch cites the opinion of law professor Terry Turipseed, who has published a paper arguing the traditional opinion that the signer of the document must be present.
Ordinarily a bill becomes law after 10 days with or without a president's signature. The only exception is when Congress adjourns within 10 days of the bill's passage, as occurred in this case. Article 1, Section 7 of the U.S. Constitution states:
If any Bill shall not be returned by the President within ten days (Sundays excepted) after it shall have been presented to him, the same shall be a Law, in like manner as if he had signed it, unless the Congress by their Adjournment prevent its return, in which case it shall not be a Law.Thus by not being present when the bill was signed by autopen an argument can be made that Obama has exercised a pocket veto, since Congress adjourned almost immediately after the bill's passage. Obama can, of course, resign the bill. And it may be that the autopen signature will be found to be valid even though Obama wasn't present.
But why risk a court fight over the issue? Obama was present and able to sign the bill. Why not sign it before going to Hawaii? Or why not have the physical bill brought to him for signing?
Someone somewhere is likely to challenge the validity of this law. It seems silly to create a mini-Constitutional crisis when there is no need for one, unless that's exactly what Obama was seeking to do.