The former DEA administrators are Bensinger, John Bartels, Robert Bonner, Thomas Constantine, Asa Hutchinson, John Lawn, Donnie Marshall and Francis Mullen. They served for both Republican and Democratic administrations.
Holder is scheduled to appear Wednesday before a U.S. Senate judiciary committee hearing. The former DEA chiefs want senators to question Holder on the legalization issue.
Advocates of legalization have welcomed Colorado and Washington's new laws, arguing that criminalizing drugs creates serious though unintended social problems. The ex-DEA heads say they disagree with that view.
After votes last fall, Colorado and Washington became the first states to legalize marijuana's recreational use — putting federal authorities in a quandary over how, or whether, to respond.
Washington state officials responsible for creating a regulated marijuana system have said they are moving forward with a timetable of issuing producer licenses by August.
Bensinger — who served as DEA administrator under Presidents Gerald Ford, Jimmy Carter and Ronald Reagan — said the supremacy of federal law over state law when it comes to drug laws isn't in doubt.
"This is a no-brainer," he said. "It is outrageous that a lawsuit hasn't been filed in federal court yet."