The Strait of Hormuz, which is closed, will remain open.

So declared Donald Trump on Monday, when the US and Iran traded military strikes for the fourth time in the space of seven days.

The IRGC, aggrieved that tankers navigating the waterway are flouting Iran’s nascent attempt to stand up a for-profit transit authority, began attacking commercial ships again last week.

Since then, at least half a dozen vessels came under fire from the Guards. The US military responded with strikes against hundreds of coastal sites in Iran, as well as rail systems, bridges and petrochemical facilities.

For their part, the IRGC ratcheted up the bombast and expanded its list of legitimate targets to include assets in Jordan. The joint command that coordinates activities between what’s left of Iran’s regular army and the Guards warned that, “Any cooperation with the US or logistical support for its military will be regarded as an act of war.”

Shipping traffic through the Strait, which recovered to nearly half the pre-war average late last month, collapsed anew. Trump, fed up with a bunch he’s described as “scum” and “crazy bastards,” among other things, reinstated the US naval blockade and suggested he might start charging tolls.

“We are reinstating the Iranian blockade, so named because it is only stopping Iran’s ships or customers from entering or leaving,” he began, in one of his social media policy pronouncements on Monday.

“All other countries will have fair and open use of the Strait” under American protection, Trump went on, before explaining that “as a matter of fairness,” the US Navy “will be reimbursed, at the rate of 20% on all cargo shipped, for any and all costs necessary to do the job of providing safety and security to this very volatile section of the World.”

This is — and I struggled in vain for a more elegant description — unimaginably stupid. Lest anyone should forget: The Strait was fully open before the war. Now, it’s doubly-blockaded and doubly-tolled.

The reinstitution of the US blockade was set to go into effect on Monday afternoon or early Tuesday. There was no immediate word on how the “process,” as Trump put it, for collecting the 20% fees would work. He said only that the “formation” of a toll-collecting system would begin “immediately.”

Trump’s infamous war MOU — a document which so self-evidently favored Iran that even this White House didn’t try very hard to spin it — is void now.

It was left to Marco Rubio to square Trump’s proposed 20% protection fees with the State Department’s official position that, “No country is allowed to charge tolls or fees on an international waterway.”