From time to time I punch holes in “progressive” myths about the Constitution and the American Founding. But conservatives and libertarians have their own myths as well.

One is that congressional authority under the Commerce Clause (I-8-3) to “regulate Commerce among the several States” permits Congress only to facilitate trade among the States—i.e., that “to regulate” means only “to make regular.” The claim is that the Commerce Clause does not empower Congress to burden or obstruct commerce—and therefore Congress has no power to ban trade in products such as obscenity, marijuana, or goods made with child labor.

This argument, like so many other constitutional claims, seems to have arisen among partisans in the 19th century, but it remains popular among some libertarians today. Its promoters observe that a major reason for the Interstate Commerce Clause was to enable Congress to smooth out barriers to trade that some states had erected against other states.

Unfortunately for us free traders, the argument is false. Congress’s power to “regulate Commerce . . . among the several States” is far wider than merely authority to make trade regular. Congress also may obstruct trade, or even ban it.

Where’s the proof?

Well, first, let’s examine Founding-Era English dictionaries. To my knowledge, not one limits its definition of “regulate” to “make regular.” In fact, of the 18 Founding-Era legal and lay dictionaries I’ve examined (counting multiple editions of the same publication as a single dictionary), NONE even includes the definition “make regular.”  Instead, definitions of “to regulate” generally include phrases such as “to direct,” “to adjust,” “to govern,” and “to determine or decide.”

Second, when you interpret a phrase in the Constitution, you have to consider not only its immediate purpose, but how people generally understood it. The phrase“regulate Commerce” is a good example. All throughout the Founding Era, Americans used those words mostly to refer to government restrictions on commerce, such as trade bans, price regulation, and prohibitory tariffs. For example, before the Revolution American colonial writers resisting Parliament’s efforts to tax them nevertheless accepted British restrictions on trade as legitimate efforts to “regulate” the trade of the empire.

Third, in the Commerce Clause the verb “regulate” has three objects, not just one: interstate, foreign, and Indian commerce. Under Founding-Era (as well as modern) rules of interpretation you should read “regulate” the same way for all three.

But a major reason for giving Congress authority to regulate foreign commerce was to enable Congress to keep out foreign goods. The idea was to encourage American manufactures and rectify an unfavorable balance of trade. And a major reason for giving Congress power to regulate the Indian trade was allow Congress to block or limit sale of certain goods to the Natives, specifically liquor and firearms.

So even though the Founders thought that an immediate use of the Commerce Clause would be to free up interstate trade, the Founders also gave Congress authority to obstruct it. This authority included power to burden or ban trade in selected items or from selected sources. And Congress could use that power for any reason not otherwise prohibited by the Constitution. Hence, even though the Constitution left direct governance over subjects like obscenity and marijuana to the states, the document gave Congress authority indirect power to affect such items by preventing them from crossing jurisdictional lines.

“Progressives” and their allies on the Supreme Court have interpreted congressional authority far too broadly. But this does not justify the rest of us committing the opposite error.