YAKIMA - Washington and the federal government are battling in court over an initiative limiting nuclear waste disposal that was overwhelmingly approved by Washington voters last month.

But it's not the first time the two sides have fought over a voter-approved measure that bars the federal government from sending radioactive waste to Washington's Hanford nuclear reservation - and the last time, the federal government won.

Supporters of the current initiative, however, contend this time will be very different.

"The legal, political and environmental landscape have all dramatically changed," said Michael Robinson-Dorn, an assistant professor at the University of Washington School of Law who is fighting to uphold the measure.

In 1980, Washington voters passed Initiative 383, which prohibited storage in the state of any radioactive waste produced outside Washington.

The federal government filed suit, and a judge ruled the measure violated federal laws governing interstate commerce and nuclear waste. A federal appeals court later upheld the ruling.

But I-383 was a "blunt tool" with a very different purpose: to force Congress to recognize that states should have a say in nuclear waste disposal, Robinson-Dorn said.

Congress responded by giving states the authority to enact compacts with each other governing waste and shipments of waste, he said.

"Even though it was overturned, it had a different purpose and it achieved that purpose," he said. "In a very real way, 383 made a difference."

No one should rule out the current initiative, he said.

Both sides are sure to cite legal cases bolstering their claims. But it is the defenders of the initiative who face an uphill battle, despite its passage, said Philip Bobbitt, professor of constitutional law at the University of Texas.

"There's no doubt in my mind that the federal government has the authority to regulate nuclear waste," he said.

The drafters of the initiative were wise to focus on mixed waste, he said, but the legal landscape hasn't changed.

"The problem is that even if that succeeds, and while that is a superior and prudent attack, the courts are not the final arbiter of intent. Congress is the final arbiter of its intent," he said. "Congress could still take it up and cram it down your throats. As a political maneuver to buy time, it may make sense. But in the end, it won't stand up."

Initiative 297, which was approved by 69 percent of Washington voters last month, bars the U.S. Department of Energy from sending more radioactive waste to Hanford until the existing waste there is cleaned up. It also places additional restrictions on waste burial and permits, among other things. Supporters of the initiative take issue with the federal government's plans for disposing of waste from World War II and Cold War-era nuclear weapons production nationwide.

The Energy Department chose the 586-square-mile Hanford site to dispose of some mildly radioactive waste and mixed low-level waste, which is laced with chemicals.

The site also would serve as a packaging center for some transuranic waste before it is shipped elsewhere for long-term disposal.

Transuranic waste is highly radioactive and can take thousands of years to decay to safe levels.

Energy Department officials have said the site's most dangerous wastes will be shipped out of state. But the state has promised to defend the initiative in court.

Attorneys for the Justice Department declined to discuss the constitutionality of the measure, citing the court fight. But the federal government appears poised to again argue that the initiative violates federal laws governing interstate commerce and nuclear waste.

This time, though, there are several caveats to the case. The drafters of the initiative wrote it specifically to bar waste imports until existing waste at the site is cleaned up, which they say does not violate federal laws governing interstate commerce.

"We're not saying it's OK if your waste is generated in Washington, you can dump it in a leaking landfill, but not if it comes from somewhere else. We're saying a leaking landfill is a leaking landfill and it's bad, so clean it up first," said Gerald Pollet, executive director of the Hanford watchdog group Heart of America Northwest, which sponsored the initiative.