What Law Enforcement Agency can I join?

Im 22,just enlisted in the military for 6 years and I would like to get into law enforcement when I get out.I will also be using this time to get a degree,getting in really good shape etc.

I would like a role that fights against one or some of these things: human trafficking,violent criminals,fugitives,armed gangs etc.

I’ll be around 28 when I get out,would this be too late to start a Law Enforcement career?