Marijuana growers cannot use federal irrigation water to cultivate cannabis, the U.S. Interior Department announced on Tuesday.

The decision could impact growers in Washington state, where two-thirds of the state’s agricultural land is irrigated by federal water.

But just how much it will affect the industry is unclear. A spokesman for the U.S. Bureau of Reclamation said the agency will not investigate growers or districts that provide water to them; instead, it will refer any violations it comes across to the Department of Justice.

Whether the DOJ penalizes these growers is yet to be seen.

, Federal Water Off-Limits to Cannabis Cultivation SitesStill, it marks a setback for marijuana cultivators in the western U.S., where the Bureau of Reclamation supplies water in 17 states.

Washington growers face the biggest hurdle, since many of them cultivate outside and are located in rural farmland. The federal government operates much of the state’s water infrastructure.

One Washington grower said she will have to dig a well in order to sidestep federal water. The estimated tab: more than $10,000. Another grower told UPI.com that the ban is merely a “nuisance” for growers, who will find alternative ways to irrigate their plants.

In Colorado, all licensed cannabis growers operate indoors – pulling their water from city and local water supplies – so the impact will be minimal.