Worker rights in trade agreements

A recent article in the New York Times discussed negotiations between Congress and the President on several pending trade acts. The Democrats of course are pushing for more protection of labor rights. The labor rights that are expressed in the bill are a ban on child and slave labor and the right to organize. The Democrats also want to include the International Labor Organization accords.
This whole debate does not make much sense to me. How is the U.S. going to make sure that these laws are enforced? Enforcing these kinds of laws would be a waste of our time needless to say inefficient. The whole point of trading with these countries is for their cheep labor which in turn makes their goods cheep. By enforcing these laws we are increasing the cost of labor. The Democrats are in a way pushing for unions. Of course the labor unions in the U.S. are supporting the Democrats in this legislation. To me it sounds a little bit like rent seeking behavior. If international labor laws are enforced then labor around the world becomes more expensive; therefore, raising the price of goods and possibly allowing unions in the U.S. to compete.