You cannot have it both ways: either Ron Paul is the ultrafederalist that he claims to be - in which case he is saying that the United States as a political entity will engage in trade only with countries that trade freely with it, while he is also saying that this government cannot forbid its citizens to spend money "wherever" they choose and "not (be) told" that there are embargoes they have to honor.
The context is the United States, as a political entity, controlling what nations it's citizens may trade with. It'll take more that comparing a couple of cherry-picked statements out of context to make a convincing argument.
That is manifestly not what the statement you quoted says and it completely contradicts the unequivocal statement I quoted - that US citizens will not be told that any nation is under embargo and that Americans may spend their money wherever they please.