In a sane world, if brought before a court, the binary itself wouldn't have any protection unless hand authored. The actual creative work/human expression was the source code. The entire point of compiling is to strip that extra data out, leaving pure functional logic that doesn't even strictly match the source logic thanks to optimization.

Then a freshly written project would be completely different with no derivative elements at all; the only commonality between the two codebases is their functional elements. You can compile a decomp into the same binary, but that's only to prove functional equivalence. The intended mode would be with a modern compiler that completely rewrites the logic (it might even have to if it writes it for a completely different computer architecture, which describes every retro console game). Then neither the source nor the compiled artifact would match.

> The entire point of compiling is to strip that extra data out, leaving pure functional logic that doesn't even strictly match the source logic thanks to optimization.

I strongly disagree with this notion from even a conceptual (much less legal) level; the point of compilation is not to erase the algorithms the programmer implemented, just to optimize and implement them.

> You can compile a decomp into the same binary, but that's only to prove functional equivalence.

This is like saying that a translated book is only "functionally" identical to the original; there's a lot of precedent in copyright law for this not being the case, and I don't think any argument revolving around the transformativeness of the compilation process would fly at all.