I know there are such laws - not sure if I agree with them, but OK (literally not sure - maybe it is good, maybe not - to be sure I wouldn't like it if it were

I know there are such laws - not sure if I agree with them, but OK (literally not sure - maybe it is good, maybe not - to be sure I wouldn't like it if it were my own company). But how are they being enforced, with so many possible candidates? Disabled people, women, different ethnic backgrounds, different schools, ex-convicts... One you go over 50, you have to have at least one of each of them? Or if you hire employee 51 and the candidate is an ex-convict, you have to hire him?