PORTLAND — The U.S. Postal Service says it’s illegal to mail materials containing advertising for marijuana products, even in states that have legalized the federally controlled substance.

The statement released this week comes in response to a letter from Oregon’s Congressional delegation asking the service to clarify its policy.

In November, a memo distributed in the Portland postal district said it was unlawful for news outlets to run marijuana ads and use the U.S. mail for delivery.

The memo caused confusion among publishers whose newspapers publish ads for the region’s dispensaries and manufacturers. Both medical and recreational marijuana are legal in Oregon.

The service says local postal officials can’t refuse mail that contains pot ads, but they must report it; the matter will then be turned over to law enforcement agencies.