For decades, the U.S. debate over drug legalization has pitted conservatives on one side against libertarians and some liberals on the other. A few conservatives have publicly opposed the drug war (e.g., National Review founder William F. Buckley Jr.), but most conservatives either endorse it or sidestep the issue.

Yet vigorous opposition to the drug war should be a no-brainer for conservatives. Legalization would not only promote specific policy objectives that are near and dear to conservative hearts, it is also consistent with core principles that conservatives endorse in other contexts.

Legalization would be beneficial in key aspects of the war on terror. Afghanistan is the world leader in opium production, and this trade is highly lucrative because U.S.-led prohibition drives the market underground. The Taliban then earns substantial income by protecting opium farmers and traffickers from law enforcement in exchange for a share of the profits. U.S. eradication of opium fields also drives the hearts and minds of Afghan farmers away from the U.S. and toward the Taliban.

Legalization could also aid the war on terror by freeing immigration and other border control resources to target terrorists and WMD rather than the illegal drug trade. Under prohibition, moreover, terrorists piggyback on the smuggling networks established by drug lords and more easily hide in a sea of underground, cross-border trafficking.

Legalizing drugs would support conservative opposition to gun control. High violence rates in the U.S., and especially in Mexico, are due in part to prohibition, which drives markets underground and leads to violent resolution of disputes. With the reduced violence that would result from legalization, advocates of gun control would find it harder to scare the electorate into restrictive gun laws.

Legalization could ease conservative concerns over illegal immigration. The wage differences between the United States and Latin America are a major cause of the flow of illegal immigrants to the U.S., but an exacerbating factor is the violence created by drug prohibition in Mexico and other Latin American countries. With lower violence rates under legalization, fewer residents of these countries would seek to immigrate in the first place.

Beyond these specific issues, legalization is consistent with broad conservative principles.

Prohibition is fiscally irresponsible. Its key goal is reduced drug use, yet repeated studies find minimal impact on drug use. My just-released Cato Institute study shows that prohibition entails government expenditure of more than $41 billion a year. At the same time, the government misses out on about $47 billion in tax revenues that could be collected from legalized drugs. The budgetary windfall from legalization would hardly solve the country’s fiscal woes. Nevertheless, losing $88 billion in a program that fails to attain its stated goal should be anathema to conservatives.

Drug prohibition is hard to reconcile with constitutionally limited government. The Constitution gives the federal government a few expressly enumerated powers, with all others reserved to the states (or to the people) under the 10th Amendment. None of the enumerated powers authorizes Congress to outlaw specific products, only to regulate interstate commerce. Thus, laws regulating interstate trade in drugs might pass constitutional muster, but outright bans cannot. Indeed, when the United States wanted to outlaw alcohol, it passed the 18th Amendment. The country has never adopted such constitutional authorization for drug prohibition.

Drug prohibition is hopelessly inconsistent with allegiance to free markets, which should mean that businesses can sell whatever products they wish, even if the products could be dangerous. Prohibition is similarly inconsistent with individual responsibility, which holds that individuals can consume what they want — even if such behavior seems unwise — so long as these actions do not harm others.

Yes, drugs can harm innocent third parties, but so can — and do — alcohol, cars and many other legal products. Consistency demands treating drugs like these other goods, which means keeping them legal while punishing irresponsible use, such as driving under the influence.

Legalization would take drug control out government’s incompetent hands and place it with churches, medical professionals, coaches, friends and families. These are precisely the private institutions whose virtues conservatives extol in other areas.

By supporting the legalization of drugs, conservatives might even help themselves at the ballot box. Many voters find the conservative combination of policies confusing at best, inconsistent and hypocritical at worst. Because drug prohibition is utterly out of step with the rest of the conservative agenda, abandoning it is a natural way to win the hearts and minds of these voters.