We believe possession and use of marijuana should be legal. That may seem like an odd way to begin an editorial urging a negative vote on Amendment 64, the pot-legalization measure, but we don’t want anyone to misunderstand the nature of our opposition.

This nation’s attempt to suppress marijuana use over the past few decades has failed.

It has squandered valuable police and judicial resources, fueled public cynicism toward the law itself and ultimately had little practical effect in keeping those who wish to use marijuana from acquiring some.

It’s long past time for the federal government — both Congress and the executive branch — to move toward a less punitive and more realistic approach toward marijuana.

Still, for a single state to legalize possession of small amounts of the drug as well as cultivation and retail facilities, as Amendment 64 envisions, is an entirely different proposition. And we think the risks are not worth the potential benefits.

Admittedly, if the federal government continues to resist concessions to growing sentiment in favor of a truce in the war on marijuana, individual states may have to defy Washington in the same way many have with medical marijuana. But we’re not prepared to welcome such a step by Colorado now, or the clash that would ensue between the federal government and this state.

For that matter, if Colorado becomes an island with legal marijuana, what’s to prevent it from also becoming a magnet nationally for marijuana users, growers and distributors?

The amendment doesn’t limit 1-ounce sales to Coloradans — nor could it in all likelihood. And while retail sales and cultivation centers will be regulated by the state, it would be next to impossible to prevent out-of-state visitors from buying several ounces at various outlets and returning home — and never mind that possessing more than 1 ounce would still be illegal.

Meanwhile, legal issues stemming from the federal-state conflict that are already visible in the medical-marijuana industry — such as how marijuana facilities conduct their banking and whether their contracts are legally enforceable — would be greatly magnified and more common.

One of 64’s biggest flaws is that it’s a constitutional amendment. Drug policy simply has no business being in the state constitution. And yet nothing prevented proponents from crafting their measure as a statute except their own suspicions — almost certainly unfounded — that state lawmakers would quickly turn around and repeal it.

To be sure, lawmakers might have tweaked the measure in a few years if it turned out to have unforeseen consequences — but that’s how the legislative process is supposed to work. As a constitutional amendment, however, any unforeseen flaws would be baked into policy for years to come.

Readers may have noticed that our objections to 64 fail to include the main argument used by the “No on 64” campaign — namely, that the amendment poses a grave risk to Colorado’s children. That’s because we don’t believe it does.

Marijuana use does pose a higher risk to teens than it does for mature adults— both in terms of future addiction and brain development. But the same is true of alcohol, which this society doesn’t ban. Instead, it enacts policies to keep alcohol out of the hands of teens.

Amendment 64 is quite clear that those under the age of 21 will have no more right to marijuana if the measure passes than they do now.

As longtime proponents of marijuana legalization, we’re obviously conflicted about Amendment 64 given current federal intransigence. But like it or not, the most appropriate venue for legalization remains the nation’s capital.