Trump recently declared that tariff is "the most beautiful word in the dictionary," and the exaltation of trade barriers has become the latest political mania. Washington hustlers are loudly promising to enrich the nation by selectively blockading American ports. Unfortunately, the Trump team and the growing horde of protectionist pundits sound clueless about America's long record of trade follies.

Instead, we are encouraged to presume that politicians merely need to issue a few commands and federal bureaucrats will instantly apply their wisdom to remedy our economic problems. But unless politicians intend to ban all imports or inflict the same tax on all imports, then government officials will need to make distinctions between products.

In the past, Customs Service employees wrestled heroically with great questions such as "Is a popcorn popper an electrothermic appliance or an electrical article?" and "Is a jeep a truck or a car?" The United States has thousands of different tariff classifications, with tariffs ranging from zero to more than 100 percent. Naturally, tariff-classification rulings are often disputed with a passion that would have made St. Thomas Aquinas proud.

Thousands of tariff categories in the past were restricted by import quotas. When Customs Service decisions change a product's tariff classification from unrestricted to restricted, the ruling can effectively ban imports.