The conservation laws are still there no matter what you do. Communism (to each according to his or her needs), somewhat not unlike the concept of paradise in the Abrahamic religions, requires a near-infinite supply of energy, which is not presently available to us humans.

People, however, are perfectly free to believe the big government will do the best possible job rationing and regulating. There does not, to the best of my understanding, exist an argument against that said belief backed by fundamental laws of nature.