Woahhs: Sure they are...but they start calling them "laws."
Doesn't work like that. Theories don't become laws. Laws and theories are different kinds of things. Laws are descriptive whereas theories are explanatory.
A law says that, under defined conditions, a system of a defined type will behave in such a manner as the law describes. A law, properly speaking, has nothing to say about why the system should behave in that way. A theory, OTOH, seeks to explain why some system behaves as it does, or has the characteristics it does, usually by proposing some causal mechanism.
A theory can never be proven because, even if it were to explain all known and relevant phenomena perfectly, it is always possible that some not-yet-known phenomena are unexplained by the theory, or would even falsify it. In addition, even if a theory is uncontradicted by any known evidence, it is always possible that there is a better theory that has yet to be thought of or proposed that would explain the known data equally as well, and more data besides (a more general theory) or one that would explain the data more elegantly (a less "ad hoc" theory).
Laws cannot be proven because of the fact that they implicitly claim universality (all systems of the defined type must be behave as the law describes) and thus can be falsified by any instance of a "misbehaving" system.
In short, proving either theories or laws would essentially require omnipotence, an exhaustive and complete knowledge of all phenomena to which they are relevant.
Laws are empirical, not necessarily universal. They are rules of thumb based upon observation. Ampere's law, for example, fails for circuits that contain capacitors. It is still called a law, however, because of how it was constructed, and it is still taught because it works well in its region of applicability.