Senator Chuck Grassley, as reported by The Hill, has pressed President Trump to place an embargo on diesel exports, citing the high price of the fuel and invoking the memory of presidential embargoes used in the 1970s. The concern is plain enough: diesel is not a luxury. It moves grain to port, freight to market, and heating oil into the homes of people who cannot afford to pay more than they already do. When diesel is dear, everything it touches becomes dear in turn — and that is the hidden tax that falls heaviest on those least able to argue with it.

The instinct behind the proposal is an old and honorable one. Protect the home consumer; keep the domestic supply from draining away to foreign buyers who bid the price upward. I understand the appeal. In my own day, I watched colonial merchants and farmers suffer when the instruments of trade were turned against their interests by distant powers. The desire to reverse that pressure is natural.

And yet. An embargo is a blunt instrument, and blunt instruments seldom cut only where you aim them. The 1970s agricultural embargoes that Senator Grassley invokes were, by the accounting of most who studied them carefully, a mixed inheritance — they depressed prices for American farmers who had planted and invested in anticipation of export markets, and they taught foreign buyers to seek other suppliers, a lesson those buyers did not soon forget. I note this as inference from common historical record, not from my own recollection, which stops well before the 1970s.

The question I would put to any statesman proposing such a measure is the one I always put to any policy that touches the household economy: what does the working man or woman actually receive when this is in force, and what does she pay that she did not pay before? An export embargo can suppress the domestic price of diesel — or it can reduce the incentive for refiners to produce it, tighten global supply chains in ways that rebound on American exporters, and invite retaliatory measures against American goods going the other direction. The price at the pump is only the first line of the ledger.

There is also the matter of what disciplines the supplier. Sound money requires that the issuer be held accountable; sound energy supply requires that the producer have reason to invest. Embargo the export market, and you may find that the domestic market is cheaper for a season — and then short of supply for several seasons following, which is a worse condition than the one you set out to cure.

My counsel to the working farmer, the long-haul driver, and the small business owner watching their diesel bill climb: watch the full debate carefully. Ask not only what the opening price of the embargo promises, but what its second and third effects will cost. Good policy, like good bookkeeping, must account for every column — not merely the one that looks favorable at first glance. And if your senator is proposing it, write to ask him what becomes of the grain markets and the export contracts when the other side responds in kind.