Is there a law to prevent global warming?

We don’t have global laws because we don’t have a global governing body. So each country is on its on. Check with the EPA. I know we have some laws about pollution, etc.

First you would probably have to prove that humans are causing it; which is a great topic of debate.

Short answer, no. Glial’s absolutely right that there are no global laws because we don’t have a global governing body. But if we did have such a body it would be very very unlikely the United States (or any other large nation) would be bound to follow such laws. For example, the United Nations can only enforce its mandates and resolutions through sanctions and, in dire circumstances, military action.

Long answer, no. If you look into the EPA, you find that it is currently embroiled in a federalism dispute between the U.S. national government and the state of California. The EPA asserts that it had a comprehensive plan for air quality and that all states must follow the guidelines it sets. As an administrative agency, its power is delegated to it from Congress. California argues that the EPA is not doing a good enough job and it wants to enact its own state-wide policy. This would interfere with the EPA’s policy, so California has been in litigation to get the EPA to allow for states’ to adjust there own policies. Which could be good and bad. A progressive state like California is likely to have a strong protections, while Texas… less so.