If the definition of insanity is doing the same thing repeatedly and expecting different results, then the United Nations has gone ’round the bend.

On Monday, the U.N. Security Council unanimously passed Resolution 2375, which imposed fresh sanctions on North Korea in response to that country’s September 3 nuclear test. President Trump, who had pushed for much starker sanctions, called the resolution “not a big deal.”

This was the 11th round of sanctions against Pyongyang in 11 years, with no change in the Kim dynasty’s behavior. At some point the international community will have to acknowledge that this approach has failed.

Part of the problem is that sanctions are not being vigorously enforced. For example, U.N. Security Council Resolution 1874, passed unanimously in 2009, authorized member states to inspect ships carrying suspicious North Korean cargo. The resolution did not expressly authorize the use of force but did compel member states to direct suspected vessels sailing under their flags to “proceed to an appropriate and convenient port for the required inspection.”

This provision has been enforced sparingly, and never by the United States. The Trump administration had circulated draft language expressly authorizing the use of “all necessary measures” to enforce compliance under the latest sanctions resolution, but this was not adopted.

Cheating is another critical issue. The day after the latest Security Council resolution was passed, U.S. Treasury officials gave a detailed briefing to the House Foreign Affairs Committee on how Chinese and Russian ships, among others, smuggle coal and other banned commodities in and out of North Korea. The smugglers’ modus operandi is for ship’s crew to turn off the transponders that track their movements when nearing North Korea, conduct their illicit business, then turn the transponders back on when clear of the country. These ships come and go from Russian and Chinese ports, where their manifests are apparently not closely inspected.

This activity underscores one of the economic laws that work against sanctions. The tighter the attempt to control trade, the more profit can potentially be made from breaking the sanctions cordon. Local officials with oversight over nearby ports cooperate for a cut of the profit, or with a wink from their superiors who have been told by higher-ups to let the smuggling continue. In essence, the United Nations has created an artificial market in which the cheaters win.

We saw the same dynamic in attempts to limit Saddam Hussein’s oil exports in the 1990s, which resulted in a billion-dollar annual smuggling operation.

A more promising avenue would be to go after North Korea’s enablers, like China and Russia. Since both countries are permanent members of the Security Council with veto power, they will not allow the United Nations to widen the scope of sanctions beyond North Korea. Indeed, Resolution 2375’s watered-down language was a result of Chinese and Russian opposition to the more robust proposal the United States put forward.

However, the United States can act unilaterally to increase the costs of dealing under the table with Pyongyang. Earlier this month Trump floated the idea of the United States “stopping all trade with any country doing business with North Korea.” This move could mean ending trade relationships with 100 countries around the world, hence was seen by some commentators as a bluff. Yet it was clearly aimed at China, which accounts for 85 percent of trade with North Korea, and is widely acknowledged as the sole country that is keeping Kim Jong Un afloat.

China angrily called Trump’s comment “unacceptable,” but Beijing should take the idea seriously. Previous U.S. presidents have been unwilling to link the U.S.-China trade relationship to the North Korean issue, but Trump has long been a critic of Beijing’s trade practices. Pushing for movement on North Korea while also criticizing China’s economic behavior is a win-win for the White House.

Trump said Tuesday that the latest sanctions “are nothing compared to what ultimately will have to happen.” As Pyongyang’s nuclear weapons become more powerful and its missiles range farther, the need for harsher measures becomes more acute. China and the other countries in Kim’s corner should understand that if they continue to aid and abet Pyongyang in its nuclear ambitions, they too will have to pay a price.