I am from North American and my question is: How can I start my own police department?

You can't start your own police department, david, your police department is a government body run by the county you are in.

Wow, put meaning to putting the law in your own hand.

You can't start your own police department, but you can start a security company called "police" or spell it different, no guns or stuff just security.

A cleaver loop hole.

You may start your own security company,