Laws are axioms. Axioms are propositions accepted true for the sake of knowing what will be the results. Many people define axioms as self evident truths, but that's 'daily life use defination'. In sciences we use the former defination although many textbooks use later one so do many people.
So Pascal's law or for that matter Newton's law are the propositions accepted true to see what will be the result.
If these results matches with many experimental observations and is able to explain many natural phenomenons rationally, then these laws are thaught in schools. But school teachers teach these laws as unlimate truth. But this is incorrect. Laws are not truth, they are just accepted propositions.
Einstein in his book,The evolution of physics, wrote:
In the whole history of science from Greek philosophy to modern physics there have been constant attempts to reduce the apparent complexity of natural phenomena to some simple fundamental ideas and relations. This is the underlying principle of all natural philosophy. It is expressed even in the work of the Atomists. Twenty-three centuries ago Democritus wrote:
By convention sweet is sweet, by convention bitter is bitter, by convention hot is hot, by convention cold is cold, by convention
colour is colour. But in reality there are atoms and the void. That
is, the objects of sense are supposed to be real and it is customary
to regard them as such, but in truth they are not. Only the atoms and
the void are real.
What Einstein meant is that the main goal of all sciences, even including philosophy, is to explain every phenomenon from 'some simple fundamental ideas and relations'(axioms).
The book I mentioned; I think wil be helpful to you: you may be having questions like How do we find these axioms? Are these laws arbitrary?(yes) and many more.