DISTRICT OF COLUMBIA:  A Gallup poll released this week showing that 58 percent of Americans support legalizing marijuana should send a clear message to Congress.

It is time to talk seriously about decriminalizing marijuana on a federal level and leaving the regulation of pot to the states. The federal government already is leaning this way on a smaller scale, agreeing to stand down in the face of pot legalization in Washington and Colorado.

But the Gallup poll showed much of the American public obviously favors this policy elsewhere. When Gallup in 1969 first asked Americans if they favored legalizing marijuana, only 12 percent said yes.

In the intervening decades, the legalization movement was often regarded as made up of libertarian crackpots. That a majority of Americans now say pot should be legal shows how much attitudes have changed. Indeed, support increased by 10 percentage points just in the last year, Gallup said.

Support for legalization, not surprisingly, was highest among the young, with 67 percent of those between 18 to 29 favoring legalization. But what’s surprising is support among Americans 65 and older, at 45 percent, has increased 14 percent since just 2011.

Medical marijuana has spread to 19 other states and the District of Columbia as people have come to accept the idea that cannabis can ease the suffering of cancer patients and those with chronic pain.

Though the federal government is not challenging pot legalization in Colorado and Washington, there still are multiple conflicts with federal law. One glaring example is in federal banking laws, which prohibit pot growers and retailers from using credit cards in their operations.

This has meant the pot industry operates almost exclusively on cash, providing temptation for criminals and making it more difficult to track sales and tax collections.

The Denver Post opposed Amendment 64 mainly because of the conflict with federal law. But we have long supported the concept of legalizing marijuana nationwide and putting an end to the massive squandering of resources on prosecuting and punishing people for possessing and using marijuana.

It appears many others now agree.