Comment by tpmoney
6 hours ago
It depends on the question you're trying to answer. The text of the US law which Citizen's United struck down remains on the books today (though has changed since it was moved to a different part of the code, so references have been updated), but the actual effective law has most certainly changed from when it was written to now. Since courts can't write or modify the law, the literal text remains, even if some of that text is effectively stricken as if the text had been removed.
If you want to know the literal text (that may or may not be enforceable), then sure a plain text diff is sufficient to know that nothing at all has changed about federal communication laws since this section was last amended in 2002. But if you want to know what the actual law is, you definitely need more than just a text diff.
See my response to the parent, but git blame solves the issue of "what did they mean" because the person (if alive) can just be asked. The same way git blame is used all the time to ask why a programmer did something some certain way, there's more to code too than just how exactly does it compile/execute. The higher level idea should be to stop legislation seemingly written by nobody, that nobody wants to answer for, but is used to make important decision about lives and livelihoods. Having courts needed to interpret verbiage that was written by living people is completely preposterous. If it's written by dead people, sure, that's a harder problem.