A coalition of 20 Colorado business organizations announced Friday it is urging the Department of Justice to enforce federal law prohibiting the use of marijuana.

Leaders of Fort Collins, Greeley and Loveland chambers of commerce as well as Northern Colorado and Upstate Colorado economic development corporations signed the letter. It urges U.S. Attorney General Eric Holder to enforce the federal Controlled Substances Act.

"Passage of Amendment 64 has left considerable uncertainty for employers and businesses in Colorado with regard to their legal rights and obligations," the letter reads.

The letters come as a response to passage of Amendment 64, which allows adults to
possess as much as one ounce of marijuana for recreational use.

The Fort Collins Chamber of Commerce is opposed to Amendment 64 because it tarnishes the state's reputation and creates legal uncertainty, CEO David May said.

"There's a lot of confusion right now in the business community in terms of their legal liabilities concerning marijuana and who has the jurisdiction," May said. "We're looking for clarity in light of the passage of Amendment 64."

The federal government's silence on the matter has caused confusion among businesses, he explained.

The coalition also sent letters to President Obama, Gov. John Hickenlooper and state Attorney General John Suthers.

The letter to the White House asks President Obama to encourage the justice department to enforce federal law.

The other letter praises Hickenlooper and Suthers for their efforts "to secure a clear signal" from Holder and the Justice Department on their intentions to enforce the Controlled Substances Act.