Would the U.S. still arm a Syrian opposition that used chemical weapons?

After a concerted effort to walk back — or at least soften — its "red line" on the use of chemical weapons by the Syrian regime, it looks as if the Obama administration may have just gotten off the hook. According to Reuters, U.N. human rights investigators now have evidence that rebel forces used sarin gas — a revelation that, if confirmed, would vindicate the president’s studied approach to the Syrian conflict and reduce the political pressure on him to act immediately.

In an interview Sunday with a Swiss-Italian television station, Carla Del Ponte, a former prosecutor for the International Criminal Tribunal for the former Yugoslavia and a current member of the U.N. Independent International Commission of Inquiry on Syria, said that testimony gathered by U.N. human rights researchers reveals "strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas." She added: "This was use on the part of the opposition, the rebels, not by the government authorities."

After the Obama administration reluctantly acknowledged on April 25 that the Syrian regime had most likely used chemical weapons, it looked as if the president had backed himself into a corner. In August 2012, Obama declared the use of chemical agents a "red line" for U.S. involvement in the conflict, later reiterating that it would be a "game changer."

How exactly the administration would respond was never made explicit, but most assumed it would trigger deeper U.S. engagement, whether by directly arming members of the opposition or instituting a no-fly zone. After all, the president warned in December: "If you make the tragic mistake of using these weapons, there will be consequences and you will be held accountable."

But when Britain, France, and Israel all claimed that the regime had indeed crossed the red line, the White House responded cautiously, downplaying what one official called "low-confidence assessments by foreign governments." Even after acknowledging in a letter to Congress that the U.S. intelligence community believes "with varying degrees of confidence" that forces loyal to Syrian President Bashar al-Assad had used chemical weapons "on a small scale," the president resolved to conduct further investigations before taking action.

The United States should not rush to judgment without "hard, effective evidence," Obama said in an April 30 press conference in which he appeared to shift responsibility for the U.S. red line to the international community. "When I said the use of chemical weapons would be a game-changer, that wasn’t a position unique to the United States…The use of chemical weapons would be a game changer. Not simply for the United States, but for the international community," he said at one point.

Despite such efforts to blur the red line — which the New York Times reported Saturday was never intended to trap the president into "any predetermined action" — the White House announced that it was rethinking its position on arming the rebels, a sort of least-worst option that would shield the president from charges of inviting rogue states like Iran and North Korea to defy the United States.

My guess is that this latest report will give the administration enough space to put plans for arming the opposition on hold. After all, what business does the United States have arming rebels who are violating international law? Even if the testimony turns out to be unreliable — something the Christian Science Monitor‘s Dan Murphy points out is entirely possible — it plays into the administration’s fog-of-war narrative that calls for a measured and methodical approach to a crisis that is increasingly difficult to read.

How Israel’s apparent success in striking Syrian missile sites over the weekend will impact the debate remains to be seen. Critics of the president, like Arizona Sen. John McCain, are spinning it as proof-positive that the United States could take out Syria’s air defenses, easy peasy, like it did in Libya. The reality is no doubt more complicated than that. Armed with additional reasons to err on the side of caution, my bet is that the administration, which has shown no interest in getting dragged into another conflict in the Middle East, isn’t about to change its mind.