What is the term for a person who worked for a number of years to repay their passage to the colonies and then is set free?

The emigrants so involved were called "indentured servants."

.Explanation:The emigrants so involved were called "indentured servants." It has been estimated that fully one-half of the immigrants to the colonies south of New England came to America under this system. Usually they fulfilled their obligations under the contracts faithfully.

trade regulation is a field of law, often bracketed with antitrust (as in the phrase “antitrust and trade regulation law”), including government regulation of unfair methods of competition and unfair or deceptive business acts or practices. antitrust law is often considered a subset of trade regulation law. franchise and distribution law, consumer protection law, and advertising law are sometimes considered parts of trade regulation law.

in general the theory of economics says that the more open to trade a country is the better   the result for the same country and the whole economies.

in real life countries impose taxes, quotas, etc which is not so good for the economies.

this kind of commercial war between the usa and china is slowing down the growth of the whole world so we can say that it is a draw back of trade regulations. and the free trade agreements are benefits of trade regulations.