The EU has won a legal battle to charge airlines for carbon emissions on flights to and from Europe.
All airlines flying to and from European Union airports will have to buy permits under the EU’s emissions trading scheme from January 1, the European Court of Justice (ECJ) ruled.
"Application of the emissions trading scheme to aviation infringes neither the principles of customary international law at issue, nor the open-skies agreement," the court said.
Wednesday's ruling was in line with expectations after a senior adviser to the court issued a preliminary opinion in October that found the EU legislation did not infringe the sovereignty of other states and was compatible with international accords.
EU Climate Commissioner Connie Hedegaard, for whom the carbon trading scheme is one of the main weapons to combat climate change, was among the first to welcome the decision. "After a crystal-clear ruling today, the EU now expects U.S. airlines to respect EU law as the EU respects U.S. law," she said in a Twitter posting. "We reaffirm our wish to engage constructively with everyone during the implementation of our legislation," she added in a statement.
Airline associations were also swift to react, warning of repercussions from non-European nations.
"We're looking at retaliation or some form of trade dispute - it could turn very messy indeed," said David Henderson, a spokesman for the Association of European Airlines.
The case was initially brought to the London High Court of Justice by the Air Transport Association of America, American Airlines and United Continental, but the London court referred it to the ECJ in Luxembourg.
Critics of the EU rules, agreed in June 2008, have argued that under the 1997 Kyoto climate pact, countries agreed to address aviation emissions jointly through the UN's aviation body, the International Civil Aviation Organization (ICAO). More than a decade on, talks at ICAO have not yielded significant progress, and the ECJ said the EU was within its rights to take unilateral action.
The EU already sets a cap on the level of emissions allowed from factories and power plants. Emitters exceeding their quotas must buy carbon permits, while those within their limits can sell any unused allowances. While emissions from most other sectors have fallen, those from airlines have doubled since 1990 and could triple by 2020, Commission figures show.
The United States, where environmental legislation has become a focus of disagreement between Democrats and Republicans, has angrily rejected the EU plan. Draft law in the US Congress, if passed, would make it illegal to comply with the EU legislation.
Jo Leinen, chairman of the Environment Committee in the European Parliament, said it would be "arrogant and ignorant" if U.S. lawmakers went ahead with their blocking legislation.
"The U.S. already had its foot on the brakes at the climate conference in Durban, and we can't allow that they now torpedo effective measures to reduce greenhouse gases," he said.
In a letter sent to EU officials last week, U.S. Secretary of State Hillary Clinton and U.S. Secretary of Transportation Raymond LaHood urged the EU "to reconsider this current course" and re-engage with the rest of the world.
"Absent such willingness on the part of the EU, we will be compelled to take appropriate action," they said in the letter.
The ruling by the ECJ, Europe's highest court, is final, although there is some flexibility in how the regulation may be applied. The EU law allows for "equivalent measures", meaning that incoming flights to Europe would be exempt if the nation from whence they came had measures in place to offset the international emissions. Airlines initially would be required to pay for only 15 per cent of the carbon they emit and would be allocated free allowances to cover the other 85 per cent.
Depending on airlines' decisions on how much to pass on, the European Commission has calculated that costs per passenger could rise by 2 to 12 euros, much less than the 100 euro per allowance penalty it would impose on airlines that do not comply.
Airlines, which have given much higher assessments of the cost, have called for a global, rather than piecemeal approach. The EU has said it fully agrees with that but has run out of patience with efforts to find a worldwide solution.
"This decision represents a green light towards an emerging patchwork of complex, bureaucratic and punitive regional schemes, which will ultimately have no impact on improving the environment and will hit passengers," Carolyn Leung, a spokeswoman of Cathay Pacific Airways Ltd, said.
Singapore Airlines said the EU was being unfair. "It could also cripple competitiveness as it offers carriers operating through hubs closer to Europe an unfair advantage," spokesman Nicholas Ionides said.
Qantas said the "patchwork approach" was flawed, but its policy was to comply with carbon law wherever it operated. A spokesman said it was still finalising policy, but anticipated costs would be passed on to passengers.