more like gang enforcer.

people usually protect their friends no matter what they do.

The union I was in, if you got caught stealing from the company, the union wouldn't help you.

Dad was a Teamster though.
At the company from which I retired, they would go to the mattresses for people who were just not real good at the job, or not popular, or a chronic, minor screw up.
But, they would just stamp "approved" if termination was for negligence causing a safety or environmental event. They were not going to defend someone who screwed up beyond a certain line.
They felt that major dereliction jeopardized everybody's livelihood.
I agreed with their positions 95% of the time in the former cases, (full admission that i disagreed with their defending some folks who never got better & didn't seem to care) and 100% in the latter.

members of local union councils or the AFL-CIO. Many such groups are "associations" or "fraternal orders".

MPLS Police Federation,well they are not recognized by the Twin Cities Labor Council. At one time decades ago,Mpls PD were Teamster 120 members,which btw,represented the bulk of Sherriff Departments as well as many State wide Police Departments.

Have been Steward, chairman of bargaining committee, President, organizer for 4 states. Police unions have to be dealt with. The culture is corrupt in most, not all but most.

I was AFL-CIO for most of my 35+ year aviation career.
Police unions are a whole different thing.
Police Protective Societies.