If Obama thought the Senate would ratify it he would sign it in a heartbeat (he voted for it at the UN) but the fact is the Senate made it clear the treaty was DOA.
Via Bloomberg News:
The U.S. won’t join the U.K., France and other major Western allies at the United Nations today to sign the first international treaty regulating the $85 billion a year global arms trade.
The absence of the world’s top arms dealer at the 10:30 a.m. ceremony in New York drawing some 60 nations casts a shadow over a decades-long push to stop illegal cross-border shipments of conventional weapons. By contrast, some of the world’s most violent nations, from drug-plagued Mexico to the war-torn Democratic Republic of Congo, will be among the signatories.
Even if the treaty wouldn’t affect U.S. domestic sales or impinge on the constitutional right to bear arms, it would be a political minefield at home. The accord wouldn’t muster enough votes for approval by the U.S. Senate, and the influential National Rifle Association, which says it has more than 4.5 million members, has lobbied against it.
“I suspect they probably took a decision that, politically, it made sense not to completely alienate people in Congress on something that, in their opinion, doesn’t matter when they sign it as long as they sign it,” said Adotei Akwei, Amnesty International USA’s managing director for government relations, in a May 31 telephone interview.
After years of stalled discussions about a multilateral arms sales agreement, it wasn’t until Obama took office in 2009 that the U.S. reversed long-standing opposition to a treaty.