Wikipedia has an edit history. You can cite a specific revision if you need to. But you shouldn’t be doing that for court cases or theses, unless it’s about Wikipedia itself.

But the same is true for other sites, they can change without notice too. You’d have to archive a copy.

But then, even in paper reference documents, what’s stopping someone from going to city hall and replacing pages in a binder? Or merely going into court and lying, saying “no THIS is the contract we signed”?