I concur wholly. There is risk no matter how you slcie this. Remember OSHA is clear it is the employer's responsibility to ensure their personnel are trained properly and are competent.
That said, one method that has worked for me (union construction organization) is testing-out employees. I have used some gewneric exams for things like forklifts, scissor-lifts, lock-out/tag-out (but not for complex procedures, I hold site meetings for these), and other topics.
I don't know if they are union or not, but at least in a union setting I know what kind of training the union has provided...thus we stay vigilant by testing. This will also provide a method for identifying gaps that you could consider further training and KSA improvement needs.
If people had common sense, I'd have a different career!