The test of garnering a filibuster-proof 60-vote majority in the U.S. Senate for climate legislation has certainly led to plenty of teeth-gnashing. But despite all the coverage of the Copenhagen meeting, one issue that has received little or no attention is how that august body would respond to whatever international agreement—either this year or next—is embraced by the nearly 200 nations involved in the exercise.
The starting point is the fact that, under the U.S. Constitution, two-thirds of the Senate, or 67 votes, are needed  to ratify any international treaty. Wouldn't that be next to impossible? “It's a good question," says Senator Bernie Sanders (I–VT). “That's a large number," agrees former senate climate aide Tim Profeta. Matt Dempsey, spokesperson for Senator James Inhofe (R–OK), who leads opposition to climate legislation in the Senate, doesn't mince words: “No way.”
But there's another way, which Congress has often used, to avoid the problem of gaining 67 votes.
First, some historical background. In 1997, by a vote of 95–0, the U.S. Senate passed a resolution  that made clear that it would never ratify the Kyoto agreement, which the Clinton Administration would sign anyway the following year. But it's not just on climate change that the Senate has been wary of international agreements. A whopping 45 treaties signed by U.S. government officials remain unapproved by the Senate , including a 1948 labor agreement, the 1994 Law of the Sea, and a 2008 convention on the recovery of child support payments. The lesson is clear: Lawmakers don't like to commit the United States to international agreements.
So does that mean any treaty coming out of the U.N. process is doomed?
It's very difficult to speculate, without knowing the text of any such treaty, about the difficulty of obtaining the elusive 67 votes. But Daniel Weiss of the Center for American Progress in Washington, D.C., imagines that it may not be as difficult as it seems. After all, he reasons, if the Senate passes some type of domestic legislation to reduce greenhouse gas emissions, the debate about whether the United States should sign a treaty would then focus on the likely actions of other countries. And having the United States on board could incentivize others to participate, Weiss explains: "Once the bill is enacted into law, approving a treaty is a way to get other countries to commit." But not everyone is as sanguine. As Senate foreign relations committee chair John Kerry (D–MA) acknowledged in June , “We may be able to pass something that puts America on track to accomplish our set of goals. But we may pass it with 60 votes, or 61 or whatever, and that’s not 67.”
There is another way to commit the United States to an international climate agreement, however, without having to clear the 67-vote barrier. It would require adopting, by a simple majority, what is known as an executive agreement. Since the 1940s, explains Nigel Purvis  of Resources for the Future, in a paper on the relevance of the subject to climate policy , the United States has approved 90% of its international deals—thousands of pacts—through so-called congressional-executive agreements. These don't require approval of two-thirds of the Senate, instead setting up a framework law that gave some level of oversight to Congress and requires fewer votes for subsequent treaties to pass. Most trade deals work this way, Purvis explains, giving Congress "a place at the negotiating table" both before and after the treaty is signed.
For a global limit on greenhouse emissions, Purvis imagines, the final domestic bill coming out of Congress might include something he calls "Climate Protection Authority." It would allow the president to negotiate an international agreement while stipulating that the Administration would submit the deal to the Senate and the House of Representatives. Each body would have to approve it by a simple majority vote.
Of course, under the Senate's arcane rules about a member's right to filibuster any pending legislation, that still means getting 60 votes. To do that, strategists might want to exclude such treaty language from any piece of domestic climate change legislation. The House bill that passed in June doesn't include such authority, and aides to key senators say it's not in the discussion right now.
Lou Leonard of the World Wildlife Fund says work by Purvis and others helped brighten up what he calls "the darker days" of the Bush Administration, when the idea of the White House ever agreeing to an international deal was considered far-fetched. But with Obama in office, there's at least the faint glimmer of possibility for an international treaty. And that might be enough to help clear any legislative hurdles, leading the way to yet another obstacle.