Universal law is the idea that everything in reality always behaves according to the same uniform physical laws; there are no exceptions and no alternatives. The notion that there is such a thing as universal physical laws is one of the great, shocking discoveries of science. Just looking at the world from a human perspective, and knowing nothing of science, it is not at all obvious that underlying the chaotic world of tangible objects that we see, there should be a perfectly regular mathematically simple structure, and yet countless experiments have shown this to be the case.
Law is arguably a misleading term here: it's not as if things are naturally free to do "what they wish" and the laws of physics are some external constraint imposed from above by force or edict. Rather, what we know as "the laws of physics" are just a compact way of expressing how we think things really are at the lowest level. Our society's current conception of the laws of physics may be violated by some novel experiment under (what we would call) exotic conditions, but that only means we were mistaken about the true universal law, which can no more be "violated" than two and two can make five: it's just not how things work.