Last night, a minor vote in a spending bill made the first crack in the foundation of the US federal government’s firm opposition to marijuana.

While an increasing number of state governments have approved medical marijuana, and Washington and Colorado have authorized recreational use of the drug, the federal government’s strict prohibition against possessing and distributing it has created legal tension and fraught circumstances for businesses. But public opinion is changing fast:

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With that in mind, last night US lawmakers performed an end run around the prohibition by passing a spending bill that forbids the Drug Enforcement Agency, the main federal organ that investigates drug crime, from spending any money on efforts to prosecute medical marijuana operations that are legal under state laws. A similar provision would need to pass in the Senate, but the bipartisan coalition of libertarian Republicans and Democrats behind the bill could well be replicated in the other house of the US legislature.

Previously, the Obama administration had issued advice to prosecutors that they focus their efforts away from pursuing state-legalized medical marijuana establishments and banks that might help them do business, but those directives lack the force of law. At their discretion, local prosecutors could still team up with the DEA in enforcement efforts, while the agency continues to promote the idea that marijuana has no medical usage.

Defunding activities, by comparison, is a fairly powerful legislative weapon: Without actually changing the law, it does everything from preventing NASA scientists from meeting with their Chinese counterparts to blocking financial watchdogs from enforcing new rules on Wall Street.

But these circumnavigations are no substitute for changing the law to make marijuana’s status as a controlled substance akin to prescription medicines or, in the recreational mien, to tobacco or alcohol. That’s the only thing that will let marijuana businesses—as well as patients using medical marijuana, people concerned with the deleterious side-effects of drug prohibition, and folks who just want to smoke a joint—operate with only a minimal level of paranoia.