And what about the phenomenon of Abandonware? I mean I don't know about home consoles, but for DOS or home computers in general, there is lots of it which is perfectly legal, right?
"Abandonware" was just a clever pirating term for any software uploading that had next to zero chance of a lawsuit or a C&D due to the company becoming defunct or the current license holders not giving a shit. Though naturally a lot of that inactivity was temporary and many of the early Abandonware sites ended up getting closed down or drastically reduced to number or available downloads.
It was a bit like a lot of those old "public domain" Amazon or Ebay sellers that would insist that a movie was public domain because it was old and citing some out-of-date or fictitious law backing them up.
So no, getting ROMs technically isn't legal, but I do it anyway. Although I would think abandonedware would be public domain.
No, because the copyright/trademark/license is still active on many of those titles. It's just that whoever has them now just isn't doing anything about it, essentially just sitting on it. That could change in the future.