Milsurp After Hours

We often hear of the efficacy of trigger locks as a safety precaution to prevent the unauthorized use of a firearm but do they work on all guns or are there some/many that can be effectively fired with a lock in place?
How hard is it to remove one without the key?

I contend that . . .

I don't know. You only have to fit them to handguns in transit here, nothing else

In the US they are issued with every retail purchase. I throw most of them away....probably ought to keep them for something but don't know what.