Eric Holder is “cautiously optimistic” about how pot legalization is going in CO and WA

"We don't want to put into the federal system low-level people who are simply there for possessory offenses," Holder said.

But Holder cautioned that the Obama administration reserves the right to sue states should they breach any of the guidelines set out by the Justice Department. In guidances issued in 2013 and 2014, Justice Department officials told states and businesses to prevent marijuana sales to minors, growing pot on public land, and any movement of the legally sold drug into the black market, among several other standards.

"We'll look to see whether or not there is a strict regulatory scheme that is in place in those states," Holder said. "What I told the governors of those states is if we're not satisfied with their regulatory scheme, then we reserve the right to come in and to sue them."

Holder's comments come nearly one month after he announced his retirement and signaled that he would support reconsidering whether marijuana should be in the same legal classification as heroin. In two weeks, two states and DC will vote on whether they should also legalize marijuana.