Counterfeiting is investigated by the FBI, drug trafficking prevention (targeted at the source, such as cartels) is handled by the DEA, human trafficking—FBI, poaching is monitored by fish and game.
There are times when a cop may have the ability to do some good now and again, but a key part of the job is harassing homeless people, busting young black guys for having some coke in their pockets, and sitting on the side of the road getting paid to aim a speed gun for a few hours. Whatever notion your friend had of being a hero is more likely to be found in almost any other law enforcement agency than the bottom level flatfoots we call the police.