To achieve that, experts say, Europe could institute a trading regime like that used to limit emissions by power plants and chemical factories.
However, participation in a CU does not necessarily represent a freer trading regime for all participating countries.
A policy of free trade, rather than membership of a discriminatory trading regime, would have maximised the benefits of tariff reductions.
They said the whole aim was a more open trading regime world-wide.
He said the step would support reformers, lock China's bureaucracy into a rules-based trading regime and contribute to stability in Asia.
And there is discontent as a result of the inequities in the global trading regime.
China stifles dissent, supplies weapons components to rogue states and does not adhere to international trading regimes, the President said.
In this respect, the deepening of EU-India bilateral trade relations supports the larger multilateral trading regime.
Russia and Ukraine will, in all likelihood, find themselves major suppliers of quotas under a future trading regime in the protocol.
Some Democrats will oppose China's formal entry into the global trading regime for the same protectionist reasons they opposed a free-trade agreement with Mexico.