Which branch of government writes laws to protect the environment?

The legislative branch writes and passes all laws, the executive branch only signs them. SO the answer is the legislative. The EPA is part of the executive, but they make regulation, not laws.

Laws = legislative

Regulation that are as powerful as a law = executuve

People that decide if the law is constitutional = Judicial

So if you want to know who made what ask yourself these questions. Does the judicial branch do this? etc. So again all laws are made by the legislative. Anything regulation is probably the executive.