OLYMPIA, Wash. - Several states have started reassessing their medical marijuana laws after stern warnings from the federal government that everyone from licensed growers to regulators could be subjected to prosecution.

The ominous-sounding letters from U.S. attorneys in recent weeks have directly injected the federal government back into a debate that has for years been progressing at the state level. Warnings in Washington state led Gov. Chris Gregoire to veto a proposal that would have created licensed marijuana dispensaries.

Gregoire, the chair of the National Governors Association, now says she wants to work with other states to push for changes to federal marijuana laws to resolve the legal disputes caused by what she described as prosecutors reinterpreting their own policies.

"The landscape is changing out there. They are suggesting they are not going to stand down," Gregoire said.

The Department of Justice said two years ago that it would be an inefficient use of funds to target people who are in clear compliance with state law. But U.S. attorneys have said in their recent memos that they would consider civil or criminal penalties for those who run large-scale operations -- even if they are acceptable under state law.

In a letter to Gregoire, Washington state's two U.S. attorneys warned that even state employees could be subject to prosecution for their role in marijuana regulation. The letter does not specify how that would happen, but the implication is that state workers who are involved in approving and regulating the sale of an illegal drug are committing a crime.

No state workers have been charged federally for regulating medical marijuana laws, and legal experts say such a move would be extraordinary -- if not unprecedented in recent history. Gregoire said she didn't want to take the chance, arguing that it would be irresponsible for her to leave her workers vulnerable.

Letters with various cautions have also gone to officials in California, Colorado, Montana and Rhode Island. Federal authorities recently conducted a series of raids at grow operations in Montana, helping push lawmakers to put stricter limits on the industry. Federal raids also targeted at least two dispensaries in Spokane on Thursday, a day before Gregoire decided to veto the proposed law.

More than a dozen states have approved the medical use of marijuana, which is not legal under federal law. About half of those states regulate medical marijuana dispensaries.

The impact of the U.S. attorneys' letters is growing. New Jersey is in the process of preparing to implement its new medical marijuana law, but Gov. Chris Christie's administration doesn't want to get operations fully up and running until it can get some clarity about the legal warnings issued in other states and how they might affect New Jersey workers and marijuana operators.

"Those letters raised serious questions about legal jeopardy," said Christie spokesman Michael Drewniak. The state's attorney general has officially asked U.S. Attorney General Eric Holder for guidance.

Gregoire said she is interested in working with other governors to push for a change in federal law to reclassify medical marijuana as a Schedule 2 substance, putting it on par with addictive but accepted drugs such as morphine or oxycodone.

Justice Department officials said in 2009 that, as a general rule, prosecutors should not focus federal resources "on individuals whose actions are in clear and unambiguous compliance with existing state laws providing for the medical use of marijuana." A memo on the subject did leave open the possibility of federal prosecution even when people comply with state law, but Holder indicated that would not be policy.

"The policy is to go after those people who violate both federal and state law," Holder told reporters at the time.

The latest memos carry a more direct warning: "We maintain the authority to enforce (federal law) vigorously against individuals and organizations that participate in unlawful manufacturing and distribution activity involving marijuana, even if such activities are permitted under state law."

Justice Department spokeswoman Tracy Schmaler said in a statement that prosecutors aren't going to look the other way while significant drug-trafficking organizations try and shield their illegal efforts through the pretense that they are medical dispensaries.

"We will not tolerate drug traffickers who hide behind claims of compliance with state law to mask activities that are clearly illegal," she said.

The federal comments have angered supporters of medical marijuana, who had believed that the Obama administration was honoring state laws. Ezra Eickmeyer, political director for the Washington Cannabis Association, said it appears prosecutors are operating under a more aggressive policy.

"Coming in and trying to strong-arm legislatures is way over the top," Eickmeyer said. "We would have expected this sort of thing form the Bush administration, but not Obama."