License people empowered by states (and federal government) to arrest people or carry firearms as part of their professional duties.
The US Constitution creates a duty for the federal government to protect civil rights†, so, it's kinda crazy that there are hundreds of thousands of people who can kill people and deprive citizens of their rights who aren't licensed by the federal government.
The federal government should be supportive of states granting licenses as they see fit with a couple obvious caveats: