Quotas. Trade quotas, in which foreign producers are prohibited from selling more than a specified number of units in the United States,also protect domestic manufacturers. To implement quotas, permits are granted by the U.S. state Department to favored firms in favored nations to sell specified amounts in the U.S. market. Note that quotas do not bring any revenue to the U.S. government as tariffs do; quotas allow the foreign firms exercising them to reap all of the benefits.