Every past administrator of the 37-year-old Drug Enforcement Administration is calling on the Justice Department to sue California if its voters decide to legalize marijuana in November.

Peter Bensinger, who ran the D.E.A. from January 1976 to July 1981, said legalizing the recreational use of pot, even in one state, would be a “disaster,” leading to increased addiction, traffic accidents and trouble in the workplace.

So, he and the eight other former D.E.A. administrators are asking the Obama administration to step in – much as it did when the Arizona Legislature passed its tough new immigration law this spring.

“The Justice Department invoked the Supremacy Clause in the State of Arizona, and in that case the laws weren’t even in direct conflict,” Mr. Bensinger said in an interview with The New York Times on Monday, referring to the portion of the Constitution that says federal law prevails over any contradictory state law.

An Aug. 24 letter to Attorney General Eric H. Holder Jr. signed by the nine former administrators points out that California’s Proposition 19 directly conflicts with the Controlled Substances Act and goes against the administration’s 2010 national drug strategy, which “firmly opposes the legalization of marijuana or any other illicit drug.”

Supporters of Proposition 19 argue that legalizing and regulating marijuana would reduce violence at the border while reaping tax revenue for financially strapped states. The administrators believe it would not bring in a substantial amount of money because anyone trying to pay taxes on the sale of pot would also be declaring themselves guilty of a federal offense.

The government, however, could end up turning a blind eye. Mr. Holder directed federal prosecutors last fall not to pursue cases against medical marijuana users and distributors as long as they comply with state law, making a federal legal challenge less likely.

“Nothing in the Constitution requires a state to prohibit as a matter of state law and prosecution what the federal government has chosen to prohibit as a matter of federal law and prosecution,” said Bruce Fein, a prominent supporter of the measure, who served in the Reagan Justice Department as an associate deputy attorney general. “Proposition 19 leaves the power of the federal government to enforce federal prohibitions on marijuana trafficking or use unimpaired.”

A spokesman for the Justice Department said it could not speculate on what it would do if the measure passes.

“The federal government is committed to enforcement of the Controlled Substances Act and the Department of Justice will continue to focus its enforcement resources on significant traffickers of illegal drugs, including marijuana, in all states,” he said.

The former administrators, who held a news conference in Washington on Monday along with several national law enforcement and substance abuse groups, have not received a response from the department.

Meanwhile, on the West Coast, two law enforcement groups supporting the measure spoke out.

“This November, Californians finally have a chance to flip the equation and put drug cartels out of business, while restoring public respect for the criminal laws and their enforcement,” said William John Cox, a former sergeant in the Los Angeles Police Department and a Los Angeles County deputy district attorney.