We all know that Gamp's Law of Elemental Transfiguration has five exceptions, the first of which is food. But what exactly is the law?
The wiki page says that:
Gamp's Law of Elemental Transfiguration is a law governing the magical world. There are five Principal Exceptions to Gamp's Law, one of which is food.
This doesn't help: What does Gamp's Law of Elemental Transfiguration state?
JK Rowling never wrote exactly what the Law states, so I can't give you that, but we can assume it from the content we have related to it. If not being able to create food out of nothing is an exception, and the wiki page also assumes that transforming animals to humans is one of the exceptions too, then it seems that the law says that "anything can be transfigured".
It seems to be something like Newton's third law that governs physics "For every action there's an equal and opposite reaction". In the case, Gamp's law would look something like "Any matter can be transfigured into anything" or "Anything can be created", having then its five exceptions of things that can't be transfigured.
Sorry for not giving something solid, but speculation is all we can have in this particular subject.
