"Whistleblower" laws prohibit employers from retaliating against employees who turn in their employers for breaking the law. They may also include "qui tam" actions, which allow whistleblowers, to sue on behalf of the government. Typically the defendant is a government contractor and the whistleblower is a current or former employee.
In the U.S., the Federal government and most states have whistleblower laws. You can find cites to the state laws in the Employment Law Yearbook, Appendix 14B (Practicing Law Institute) and the National Survey of State Laws. The state laws themselves are available in each states statutes, and they are compiled in the Appendix to John T. Boese's Civil False Claims and Qui Tam Actions (Aspen Publishers).
Environmentally-related whistleblower laws are usually enforced by the United States Department of Labor.
John T. Boese's Civil False Claims and Qui Tam Actions (Aspen Publishers) is a leading whistleblower treatise.