Free trade refers to the power of a free market to provide compelling reasons to pursue peace rather than war. Paul obviously feels it has to be adjusted to adequately deal with what he sees as impediments to this free trade process. I am not supporting any particular adjustment he feels is necessary - I'm just saying that he's pushing, overall, for trade as a war replacement power, versus socialism.
The guy is a kook. He criticizes Israel for defending themselves, criticizes America for trading with Israel, and then compares palistinain terrorists to concentration camp victims.
Ah, so sad that he's fallen for the tinsel false god of Free Trade. History is loaded with heavily trade inter-dependent nations that have ended up killing each other anyway. Trade as a means of achieving peace has long since been proven a failure. It even causes you to be more involved in war than less, since as your economy becomes more dependent upon foreign nations, so does the need to protect them with your military grow. This is what over-extended and collapsed the British Empire. Unnecessary trade, especially in anything military critical, is a weakness that attracts enemies. That's why it didn't take long for the Founders to realize that protectionism was the only effective way to build a nation and keep it intact in the long term.