Are there good arguments against unrestricted free trade?

Adam Smith in The Wealth of Nations laid out the basic argument in favor of free trade. The law of comparative advantage says that production is maximized if each area produces what is most profitable to it.

One opposing argument I came across says that comparative advantage can change over time. A developing nation could use protectionism to allow an industry to grow to the point where it will achieve comparative advantage.

Many people point to sweat shops and unfair working conditions as arguments against free trade. I am not sure if these are valid arguments against free trade so much as arguments against inequitable working conditions.