Some international disputes are significant for symbolic reasons, others for substantive ones. The current conflict between the United States and the European Union over airline-emissions limits is both. Unfortunately this means that the U.S. is doubly on the wrong side. The Obama Administration ought to be applauding the Europeans. Instead it’s threatening a trade war.

The conflict over the limits, which are scheduled to take effect on New Year’s Day, has been brewing for nearly fifteen years. In highly condensed form, it runs as follows:

Back in 1997, when the Kyoto Protocol was drafted, it included a directive for nations to work together to reduce greenhouse-gas emissions from air travel. (Currently, aviation emissions account for only three perc ent of global CO 2 emissions; however, that figure is expected to grow dramatically in coming decades.) The International Civil Aviation Organization, or I.C.A.O., was asked to come up with rules that its membership, which includes virtually every nation in the world, could agree to.

Perhaps not surprisingly, given the generally dismal record of such negotiations, the I.C.A.O. failed to come up with such rules. Several years ago, it officially gave up trying. At that point, the E.U. decided to step up to the proverbial plate. The European Parliament passed a law requiring airlines that fly in and out of Europe either to live within an emissions allotment or to purchase credits on Europe’s carbon market. (Essentially, the E.U. is just adding the airlines to its existing emissions trading system.) When fully implemented, the requirements should reduce greenhouse-gas emissions each year by the equivalent of taking thirty million cars off the road.

Obviously, European carriers will be the ones most significantly affected by the new requirements. Still, even the marginal costs that the rules would impose on U.S. airlines were deemed—by them, at least—to be too high. In a wonderfully cynical move, U.S. carriers worked particularly diligently to ensure that the I.C.A.O. would never issue emissions limits, then turned around and challenged the E.U.’s rules on the grounds that only the I.C.A.O. should be able to issue such limits. United Airlines, American Airlines, and the Air Transport Association of America went so far as to challenge the E.U.’s rules in court, but, in a decision handed down earlier this month by Europe’s highest court, in Luxembourg, they lost.

That should have been the end of things—were the positions reversed, the U.S. would clearly expect the Europeans to abide by a Supreme Court ruling. But no. Two weeks ago, Secretary of State Hillary Clinton and Transportation Secretary Raymond LaHood wrote a letter to E.U. commissioners, demanding that they suspend the rules, or else.

“Absent such willingness on the part of the E.U., we will be compelled to take appropriate action,” the pair wrote. It’s not clear exactly what “appropriate action” they meant, but the transportation secretary possesses the power to impose retaliatory sanctions on foreign airlines. Meanwhile, the House of Representatives has approved a bill forbidding U.S. airlines from complying with the E.U. rules; the Senate is considering a similar measure.

It’s bad enough—more than bad enough, really—that the U.S. has failed to lead the fight against climate change. This is very nearly as true under President Barack Obama as it was under George W. Bush. As former Senator Tim Wirth, now the president of the U.N. Foundation, put it recently, “I don’t know who and where the climate leadership in the Administration is. It doesn’t exist.”

Now, by trying to block others’ attempts to tackle the problem, the U.S. is behaving in a manner that seems best described as unforgivable. Last week, in a letter to Secretaries Clinton and LaHood, the heads of several of the nation’s leading environmental groups noted that the Administration is “actively thwarting other countries’ efforts to effectively and efficiently reduce greenhouse gas emissions,” a position that is incompatible with the Administration’s own stated commitment to avoiding “a dangerous rise in global average temperatures.” The groups urged the Administration to abide by the European court’s decision, “just as the Administration would wish other nations to respect the decision of the U.S. Supreme Court.”

It’s pretty much impossible to imagine how the world can reduce the risks of climate change without imposing some sort of emissions limits, and airline emissions seems like as good a place to start as any. If the Administration disagrees with the European plan, then it would seem to be under a heavy obligation to propose its own. All it's doing now is shilling for the airlines. Is this any way to run a planet?

Photograph by Scott Barbour/Getty Images.