Specialised environmental crime units composed of people trained in environmental inspection and criminal investigation have been used in several States with great success. Usually, the enforcement authority of the environmental crime unit overlaps and exceeds the authority of its civil or administrative counterpart. In many cases the units collaborate, utilising the expertise of both. In the United States Environmental Protection Agency (EPA), example provided below, the environmental criminal investigations agents are sworn federal law enforcement officers with statutory authority to conduct investigations, carry firearms, make arrests for any federal crime and to execute and serve a warrant.
Some States have also developed honorary, voluntary, or informal environmental police or wardens, particularly to regulate natural resources in remote areas. A few examples are discussed following Guideline 41(k)
on public participation in enforcement.