President Obama’s executive orders in respect of Ukraine remind us of the embargo America once ran against the communist regime in North Vietnam. That was during the Indochina war, when we blocked all Vietnamese accounts in American banks in America and in American branches of foreign banks. Also in foreign branches of foreign banks if the banks had branches in America. And in foreign branches of foreign banks even if the banks didn’t have branches in America, so long as the accounts were denominated in dollars. We still lost the war, a reminder that military power and political will trumps the lawyers.

Important differences lurk between the predicament in which Ho Chi Minh found himself in the 1960s and President Putin finds himself today. Uncle Ho, as the communists called him, had, in Russia and, to an extent, in Communist China, the equivalent of a banker and a supplier. Plus, the Europeans had fallen away from America’s and freedom’s cause in Vietnam. So the Vietnamese communists had plenty of ammo and other supplies with which to mount their attack on Free Vietnam, a country hungering for the kind of democracy Ukraine wants.

So what kind of support will Mr. Putin have and against it how aggressively will Mr. Obama use the legal arsenal he and Congress are putting in place? In theory the sanctions regime is formidable, starting with the executive order Mr. Obama inked March 6. It blocks the property of “persons who have asserted government authority in the Crimean region without authorization of the Government of Ukraine.” It labels as an “extraordinary threat” to America those who undermine Ukraine’s peace, stability, and sovereignty and contribute to the misappropriation of its assets.

It’s hard to think of language that broad since the Alien and Sedition Acts, which stunned America when they were passed by the 5th United States Congress and signed by President John Adams. That was in 1798 during our almost war with France. That was different from Mr. Obama’s executive order, or the Sovereignty, Integrity, Democracy, and Economic Stability of Ukraine Act of 2014 that is now moving through the Congress. The Alien and Sedition Acts set the stage for arrests and jailings. The breadth of their language, though, was similar.

Mr. Obama’s order applies to those whom the treasury secretary, Jacob Lew, deems to be in violation of its terms. Mr. Obama this morning named 11 such culprits, including an aide to President Putin, Vladislav Surkov; the deputy prime minister of the Russian Federation, Dmitry Rogozin; and the fugitive president of Ukraine, Viktor Yanukovych, who urged a Russian invasion. Mr. Obama has blocked all their property and interests in property that “are in the United States, that hereafter come within the United States, or that are or hereafter come within the possession or control of any United States person (including any foreign branch).”

The sanctions put them in the line of fire of the Office of Foreign Assets Control and of one David Cohen, the Treasury undersecretary for “terrorism and financial intelligence.” Cohen was described by one savvy market adviser, in a cable to clients Sunday, as “a ninja warrior of global finance: you mess with him at your peril.” He has blocked Iranian money, Mexican drug cash, and, as this adviser put it, “plenty of other things we don’t read about.” But the targeting by Mr. Obama of 11 marginal individuals suggests a tentative test of the powers of economic warfare.

Whether the Kremlin fully comprehends what could happen in a maximalist approach is not so clear. The Fed disclosed last week that $104.5 billion in American government securities was removed from custody of the Federal Reserve Bank of New York. The analyst who warned of the ninja warrior in the Treasury characterized the market’s conclusion as being that “this was the Central Bank of Russia reacting to President Obama’s March 6th executive order.” But he also characterized as “dead wrong” any supposition by the Russians that they could dodge the Treasury ninjas by moving custody to a different bank.

That’s because such securities are by definition always under American jurisdiction. It may be that the collapse in the value of the American dollar in recent days — it dropped briefly below a 1,390th of an ounce of gold Sunday— is signaling a flight by Russia to a money that is not so automatically within the reach of sanctions. Or it may be that the relatively modest movement in gold means the Russians aren’t afraid of what they’ve seen from Washington so far, a view that would be in accord with an analysis reported by the Daily Beast’s Eli Lake this morning.

He and another Daily Beast leg, Joshua Rogin, quote an analysis by a firm called Macro-Advisory, which operates at Russia and reckons the starting sanctions against Russia would be in the near term only an “inconvenience.” That analysis characterizes as “disruptive” more drastic measures that would include “going after Russia’s ability to interact in global financial markets. It reckons only restrictions on Russian energy exports or trade sanctions would be “catastrophic.” So at the moment it seems that Mr. Obama is repeating the big error of Vietnam, gradual escalation — at the end of which we, as Mr. Obama has done in respect of Iran, flinched.