Sen. Bernie Sanders (I-Vt.) speaks during the first day of the Democratic National Convention in Philadelphia on July 25. (Paul Sancya/AP)

Sen. Bernie Sanders of Vermont led a chorus of critics after the Drug Enforcement Administration declined to allow the use of marijuana for medical purposes — the latest example of fast-changing politics in the war on drugs.

"People can argue about the pluses and minuses of marijuana, but everyone knows it's not a killer drug like heroin," Sanders wrote in a tweet, after the DEA announced that marijuana would remain a Schedule I drug with "no currently accepted medical use in the United States."

He was echoed by Democrats from mostly blue states and districts, who criticized the DEA for not going further to remove marijuana from the legal blacklist.

"The DEA should be spending its limited resources on targeting high priority narcotics rather than erecting roadblocks to medical marijuana," Rep. Ted Lieu (D-Calif.) said in a statement.

"The Drug Enforcement Administration’s decision to keep marijuana as a Schedule I drug is frustrating, unscientific and, frankly, out of touch," said Rep. Jared Polis (D-Colo.) "It is ridiculous to classify marijuana alongside other Schedule I drugs like heroin. This is further evidence that it is past time that Congress legalize and regulate marijuana like alcohol, using Colorado as an example."

On Twitter, several Democrats made the point more succinctly.

Sen. Jeff Merkley (D-Ore.), the lone member of the Senate who endorsed Sanders's presidential bid, argued that the DEA's decision continued to leave states such as his in a legal penumbra.

"In Oregon alone, it is estimated that the marijuana market could bring in close to half a billion dollars in revenue, all in cash, during its first 14 months of legal sales," said Merkley. "The federal government shouldn’t force Oregon’s legal marijuana businesses to carry gym bags full of cash to pay their taxes, employees and bills. Expanding access to marijuana for research is helpful, but doesn’t solve these problems.  It’s clear now that Congress must take action to end the confusing patchwork of state and federal laws and regulations so that businesses in states that have legalized medicinal and recreational marijuana can access banking services, additional federal research can be conducted, and Veterans Affairs doctors can finally discuss medicinal marijuana with patients.”

As a candidate for president, Sanders took a high-profile stance in favor of "de-scheduling" marijuana to allow state experiments with legalization and to remove the threat of jail time for people who used it. In the run-up to California's primary, Sanders said that if he had a vote in the state, he'd support a ballot measure that would legalize the sale of the drug for recreational purposes. (For 20 years, marijuana has been available for medicinal purposes in the state.)

"'I find it very strange that a major financial institution that pays $5 billion in fines for breaking the law and not one of their executives is prosecuted, while kids who smoke marijuana get a jail sentence," Sanders said in many of his speeches.

And in July, when delegates met to firm up the Democratic platform, pro-Sanders delegates won language in favor of de-scheduling marijuana. That plank, passed by a single vote, marked the most significant statement in favor of legal marijuana since the start of the war on drugs.