Nowhere in the Constitution is there powers enumerated to police. The Sheriff in any given county is the highest law enforcement officer because he is elected by the people.
I'm in a tough spot personally. I have family who are law enforcement. Who I know to be good people. But are working within a corrupt system.
The Police State.
Doesn't matter if it was in the constitution or not, it's illegitimate anyway.
Your friends and family are probably good people, they just don't know they're the actual criminals, when they invade other's rights. You should tell them about the libertarian platform, Adam Kokesh's book "Freedom!" might be a good start.
Funny story. My brother (who is a cop) gave me an Amazon gift card for my birthday last month. I used it to buy The Most Dangerous Superstition by Larken Rose. Haven't started reading it yet. Will have to check out that Adam Kokesh book as well.