For half a century, presidents of both parties treated the Strait of Hormuz as an American obligation to be met and never invoiced. Last Monday, President Donald Trump broke the pattern: the United States, he announced, will be “THE GUARDIAN OF THE HORMUZ STRAIT” and will be reimbursed for the job. “We guarded it for nothing,” he told Fox News, “and now we’re going to guard it, we’re going to get paid for guarding it.”

Commentators rushed to pick apart the mechanics of a transit fee. They are missing the doctrine underneath it, which is overdue and correct: the era of securing other people’s oil at American expense is over.