Indian tribes are allowed to grow marijuana on their lands and sell it, the U.S. Justice Department announced on Thursday.

The department did clarify tribes have to follow the same federal conditions on marijuana use for states that have legalized the drug.

Oregon US Attorney Amanda Marshall said the Justice Department policy answered questions raised by tribes about how legalization of pot in states like Oregon, Colorado and Washington would apply to Indian lands.

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Marshall said the policy raised other questions. "What will the US as federal partners do to assist tribes in protecting our children and families, our tribal businesses, our tribal housing? How will you help us combat marijuana abuse in Indian country when states are no longer there to partner with us," she asked.

Whether tribal marijuana would catch on as a cash cache like tribal casinos is a big question. The Oregon US attorney said only three tribes -- one each in California, Washington state and the Midwest -- have signified interest. She declined to identify them.

Seattle attorney Anthony Broadman, whose law firm represents tribal governments throughout the West, said the economic benefit can be big. "If tribes can balance all the potential social issues, it could be a really huge opportunity," Broadman said.

But some people living off Indian lands are wary of worsening existing drug and alcohol problems by growing and selling cannabis.

The Yakama Nation in Washington state recently banned marijuana on the reservation and it is trying to stop state regulated marijuana sales and cultivation on lands off the reservation where it still holds hunting and fishing rights.

The Hoopa Valley Tribe in Northern California has battled illegal pot plantations on its reservation that have damaged the environment.