Obama has only to sign it to slap handcuffs on what the Congress can do by way of legislation.
It would forestall (or give two-faced RiNO's an excuse to beg off on), e.g., a national 2A act mandating concealed carry in all jurisdictions at all times (for the sake of argument). It might actually be citable by SCOTUS as a reason to overturn state open- and concealed-carry laws, and to sustain Illinois-style restrictive legislation.
It would act as a drag, if it were frequently invoked by Chamber and RiNO types, who are secretly or not-so-secretly anti-2A (according to something I saw about the 1999 Pew sociology and political typology study, of which a new 2009-2010 version is out and available for inspection), on any proposed civil-immunities legislation referring to RKBA.
You know some liberal jurisprudence has been "setting us up the Bomb" for repeal of 2A for years now, beginning with a frank reading of 2A, 5A, and 14A's "privileges and immunities" clauses (the amendments cited in the Emerson case brief and the district court's original opinion in favor of Dr. Emerson), to reach an expansive statement of RKBA, for the ulterior purpose of energizing grabbers to undertake repeal of 2A. (And they might as well take down the rest of their "living Constitution" and its BoR that is such a party-poop whenever people start talking about running "His Won-ness" for a third term, and/or for "President for Life".)
I agree with you, that the next Republican Senate should bring up all these UN treaties and crush them underfoot, to stop this kind of footsie-playing with the international totalitarians.
I would point out, however, that the GOP majority from 1994 to 2006 didn't lift a finger to see about scotching this garbage when they had the power.