Attorney General Eric Holder vowed to continue enforcing federal laws against marijuana in California even if the state's voters legalize the drug.

Holder, in a letter to former administrators of the Drug Enforcement Administration (DEA), officially stated opposition to Proposition 19, the state ballot initiative on which Californians will vote that would legalize, tax and regulate marijuana.

"We will vigorously enforce the [Controlled Substances Act] against those individuals and organizations that possess, manufacture or distribute marijuana for recreational use, even if such activities are permitted under state law," Holder wrote in the letter, which was reported on by The Associated Press.

The letter sets up the prospect of a showdown between the Obama administration and California over pot if voters approve the ballot initiative.

Polls have suggested that such an outcome is, at the very least, a possibility. Fifty percent of registered California voters said in a late September Field Poll that they favored Prop. 19, with a net 46 opposed to it in varying degrees. A Reuters/Ipsos poll released in early October, however, suggested broad opposition to the measure, with 43 percent of Californians in favor of legalization and 53 percent opposed.

President Obama himself has been on record as opposing the legalization of marijuana, though his administration has generally left alone facilities in states with medical marijuana laws. A top Republican, Rep. Lamar Smith (Texas), has said the administration's stance encourages use of the drug.