Adam Smith argues against the regulation of commerce because he feels that it is inefficient. Smith believes that economies become more efficient as they develop a division of labor. This allows a given person to specialize in one thing and become very good at doing that one thing. The same goes for countries. He argues that it is advantageous for all countries to specialize in those things that they are best at. If every country does this, countries can trade with one another (assuming there is no regulation). They can produce what they are best at producing and trade with others to get the things they are not good at producing. This is more efficient than having every country try to produce everything for itself.