1) Any individuals who take care of problematic people through violence. They hit hard and fast either out in the open or covertly.
2) Can also be used as a verb to describe carrying out the action of a regulator.

Someone who solve problems using necessary violence, wich is of course necessary in a lot of cases.

People who Bring authority to a chaotic situation.

The Regulators was the name of the group of cowboys headed by Dick Brewer and Billy The Kid in New Mexico in the late 1800s. Regulating refers to the regulation of any stealing of cattle from their ranch.

The story of the Regulators was made into a movie called Young Guns where the character Charlie Bowdre famously says “We work for Mr Tunstall as Regulators, we regulate any stealing of his property, we’re damn good too.”

This sample was later used in the song “Regulate” by rapper Warren G.

Regulators
We regulate any stealing of his property
And we damn good too
But you can't be any geek off the street,
Gotta be handy with the steel if you know what i mean, earn your keep!