In the US, if I say I'm a lawyer, I'm at least implying that I passed the bar in some state (although possibly not in your state). If I just went to law school or if I just read a few books on constitutional law, it wouldn't be normal to describe yourself as a lawyer and you wouldn't be legally allowed to represent yourself as one.

People who have even grad degrees in some branch of engineering and have been working in the field for decades. But simply have never had a reason to get a PE? Perfectly reasonable for them to describe themselves as engineers (but not, of course, as PEs).