The decision will not immediately affect the country’s cartels, or the rising (once again) levels of drug-related violence and corruption. It will, however, eventually bring down marijuana prices, which over time will damage the cartels’ business. And if President Enrique Peña Nieto wishes to continue the drug war, the decision will free him to concentrate on heroin and methamphetamines (produced in Mexico) and cocaine (brought from South America).

For the country’s always prickly ties with Washington, Mexico’s Supreme Court ruling could cut either way. If hard-liners in the U.S. — the Drug Enforcement Administration and its supporters in Congress — determine the American response, there will be trouble.

Washington can insist on Mexico honoring a strict interpretation of United Nations conventions against all drugs, including marijuana. It can pressure Mexico, as it has done in the past, to keep intercepting marijuana shipments to the U.S., uprooting marijuana plantations, searching for tunnels across the border and jailing young people for nonviolent drug offenses.