A question that interests me is, how many of the 21 GOP representatives who signed this letter actually have doubts about the constitutionality of bills signed by a presidential auto pen? As a legal matter, the claim that such a practice is unconstitutional is frivolous, for at least three reasons. First, as this neurotically comprehensive treatment of the issue by the OLC demonstrates, there wasn’t even a common law requirement at the time of the Constitution’s drafting that “signing” a document meant “signing it personally.”
Second, as the OLC memo also points out, nobody has ever argued that bills have to “presented” to the president by literally handing them over to the POTUS, or that the president has to walk over to Congress to “return” a vetoed bill.
The OLC memo doesn’t mention the most ridiculous aspect of this issue, which is that presidents don’t even need to sign bills at all (if Congress is in session, a bill that isn’t affirmatively vetoed becomes law in ten days whether it has been signed or not).
My guess is that a few of the letter’s signatories are representatives of the kind of magical legal thinking one finds on the far right, where Militia Men argue that the federal income tax is unconstitutional because Ohio wasn’t “really” a state at the time the 16th amendment was ratified etc. etc.
Most of them, however, are probably indulging in yet another cynical de-legitimation ploy, giving their constituents just one more reason to believe that Obama is somehow not exactly a real president, doing real presidential things.