"... any new theory (especially one which makes outstanding claims) has to have established scientific laws to support it."
***We both agree, sorta. I would readily accept your statement if the word "law" were substituted with the word "evidence". That word, "law" causes trouble in these kinds of discussions because people start using it as if it really did mean "law". In scientific method, a law is just an observation. Newton's law of gravity doesn't mean everything has to "obey" that law, it is just an observation of how gravity behaves, with a nifty mathematical description. Note that we do not call it the "theory of gravity" because a theory explains why... and we really don't know what causes gravity at this point. When physicists started noticing that at the atomic scale, Newtonian "laws" were no longer applicable, a new observation was introduced as a correction factor to physics, thanks to Einstein. It was widely discussed and supported because there were observations that no longer fit the Newtonian mold and, it was brilliant physics. Exactly what scientific "laws" did NOT support plate tectonics at the time it was proposed?
"I've read "Worlds in Collision" by Velikovsky and all of his physical predictions are invalidated by the well established laws of physics that I've studied up through college."
***I read it too, and I also studied somee physics in college, welcome to the club. Again I would quibble with your use of the word "law". I agree that Velikovsky's predictions and theory did not pan out for the most part. But his predictions were not invalidated by "laws" of physics, they were invalidated by direct empirical observation. Some people thought Velikovsky was ahead of the game when it was verified that Venus was indeed very hot (contemporary cosmology said that it would be a cold planet), but he was probably just lucky.
"Just as one example, his theory that Venus could pass by the Earth and cause the Earth's rotation to stop and then restart is nonsense according to the laws of thermodynamics and conservation of angular momentum, among others, and there are no known forces that could explain such an event."
***Again you're using the word "law" in a way that doesn't really help the discussion along. If I do the "law = observation" substitution, I would probably agree with you. The fact that there are no KNOWN forces which could explain it is exactly the point. It is postulated as an UNKNOWN force, possibly stronger than gravity, which is after all a relatively weak force. But that's one thing I like about bold theories -- they should be easy for experts to point out the obvious flaws. I'm no cosmologist.