THE federal Bureau of Reclamation is in the water business, not the law-enforcement business. That’s an easy distinction to remember, except when it comes to marijuana, which continues to tie the federal government in knots.

With 16 Eastern Washington dams, and sprawling Columbia Basin and Yakima projects, the bureau is the wholesale water supplier for 1.2 million acres of irrigated farmland in the state. Without it, the bread basket of Washington would be desert.

Despite that role, the bureau has never had — nor should it have — a stake in what crop is planted. That’s a basic tenet of the 1902 National Reclamation Act, which created the bureau and transformed the arid American west.

Yet the federal government is now threatening to forget that history, because some regulators are queasy about Washington and Colorado’s experimentation with marijuana legalization.

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At the request of the bureau, the U.S. Department of Justice is reviewing whether federal water can be used to irrigate planned marijuana cultivation sites in Eastern Washington. A decision is expected soon.

This is an important issue, because state-licensed marijuana growers are eager to grow outdoors in Eastern Washington. Sun-grown marijuana requires less electricity, making it more environmentally friendly than indoor crops.

The DOJ’s decision-making should be simple. It has already issued memos directing federal criminal prosecutors and banking regulators to stand down from obstructing state-licensed marijuana merchants, so long as those businesses are good actors, and in good standing.

Follow that precedent, and the water should be a nonissue.

But the water issue, according to Tim Personius, the Bureau of Reclamation’s deputy director of the Pacific Northwest region, is complicated by contracts between the bureau and local irrigation districts. Those contracts require the districts to comply with federal law.

Once again, another complication caused by the multistate revolt over federal marijuana laws could be resolved by Congress. The “Respect State Marijuana Laws Act of 2013” bill, H.R. 1523, is supported by Washington’s U.S. Reps. Adam Smith, D-Bellevue, and Jim McDermott, D-Seattle. That bill, however, hasn’t moved since it was introduced.

Instead, these conflicts get kicked to the DOJ. It should follow its own precedent and keep the Bureau of Reclamation’s role clear: Its hand is on the water tap, not on a holster.

Editorial board members are editorial page editor Kate Riley, Frank A. Blethen, Ryan Blethen, Sharon Pian Chan, Lance Dickie, Jonathan Martin, Erik Smith, Thanh Tan, William K. Blethen (emeritus) and Robert C. Blethen (emeritus).