The House approved an amendment to the transportation spending bill last night that would block federal funds from going to implement the European Union Emissions Trading System in a move that one foe of the measure says could be a "nothingburger."

While policy riders on spending bills are a time-honored way for Congress to influence administration policy, the E.U. amendment to the transportation bill, H.R. 5972, from Rep. Chip Cravaack (R-Minn.) targets an issue on which Republicans and the Obama administration agree: that U.S. airlines entering European airspace should not be subject to the E.U. Emissions Trading System.

The amendment's impact is unclear. It would bar appropriated funds from going to implement the E.U. program, but the system applies to private airlines, not to government agencies.

Annie Petsonk, the international counsel for climate and air at the Environmental Defense Fund, which supports implementation of the E.U. program, said the Cravaack amendment could be a "nothingburger," or it could have wide-ranging effects that its sponsors do not intend.

"I wasn't aware that there were any federal funds involved," Petsonk said in an interview.

Petsonk said, however, that the rider could be interpreted to bar the Department of Transportation funding from being used in any way that might further the E.U. emission program, including by boosting the efficiency and reducing the carbon footprint of flights in U.S. airspace.

"Arguably, any federal funds that are used to do things like improve air traffic control and therefore help reduce emissions, or funds for research and development for improved efficiency of aviation, could fall into this prohibition," she said.

Congress has no power to amend E.U. law, she added, so U.S. airlines would still be liable for fines and penalties if they refuse to comply with the program for flights to Europe.