By Jonathan Kaminsky

OLYMPIA, Washington (Reuters) - The regulatory board overseeing marijuana legalization in Washington State is leaning toward allowing licensed growers to raise the drug outdoors, citing the much higher carbon footprint of indoor and greenhouse cultivation, board members said.

The view, which all three members of the Washington State Liquor Control Board told Reuters they shared, represents a reversal from the draft pot industry rules the body issued last month.

"If they can provide the security parameters that we require for indoor or greenhouse, if they can provide for that outdoors, then it's OK with me," board member Ruthann Kurose said, after a public meeting on Wednesday.

Washington and Colorado became the first U.S. states to legalize recreational pot after approval by voters last November, although the use and sale of marijuana remains illegal under federal law. Some 18 states allow pot for medical use.

The shift on cultivation rules underscores the degree to which the Washington State board is taking public feedback to heart, Chairwoman Sharon Foster said, and comes after the Seattle Times cited a 2012 study published in the journal Energy Policy saying that a kilogram of cannabis grown indoors requires the same amount of energy as 11 cross-country car trips.

"We're all willing to keep learning and changing our minds when enough stuff is put in front of us," Foster said.

The next draft of the pot industry rules is due on July 3. The board will file its official rules in August and plans to start accepting applications for licenses to grow, process and sell marijuana in September. Retail marijuana stores are expected to open in the state next spring.

While marijuana remains illegal under federal law, it is unclear whether the Obama administration will move to block states from implementing their recreational markets.

On Monday, seven Democratic members of Congress from Washington State sent U.S. Attorney General Eric Holder a letter urging the federal government to respect state law and to quickly announce its intention to do so.

"Further delay will slow the potential for economic advancement and could lead to wasted resources," the letter said.

(Editing by Cynthia Johnston and Leslie Adler)