Try looking for civilian jobs in the Department of Defense through the federal jobs page.
Many military people go into civilian law enforcement.
Environmental police units have formed in several states, including New York and Massachusetts . The state government jobs page has links to official listings of state jobs. Be aware that most, if not all, states have hiring preferences for qualified military personnel. Information about the preferences is usually contained in the application forms, most of which are downloadable. Become familiar with veteran hiring preferences in the federal government.