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.

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!