What do I want to do with my degree

Ever since I was young I knew I wanted a career in Law Enforcement, now almost being done with college I would like to either go into the United States Coast Guard, or the Marines. I want to go into one of these branches because I know with the training and experience I would get may give me a better shot into becoming a A.T. F agent. I want to go into the A.T.F (Alcohol, Tobacco and Firearms and explosives) because these federal agency are in charge of stopping the illegal market on firearms, are in charge of stopping the sell illegal sell of alcohol, and tobacco as well of arson or and explosives. These branch is really goes under seen because many people focus on the FBI, CIA, DEA, but the ATF is also an important branch when it comes to the safety of U.S Citizens, stopping domestic terrorism.