Who would've thought we'd reach this point in the marijuana legalization movement? The leading Democratic presidential candidates agree that the U.S. should reform its marijuana laws, but they disagree about how far that reform should go.

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On Saturday, frontrunner Hillary Clinton called for the loosening of federal drug laws, arguing that the federal government should allow more research of marijuana by rescheduling it under the Controlled Substances Act.

But Bernie Sanders responded, saying that Clinton has "ignored the major issue."

Later that day, Sanders, Clinton's top opponent for the Democratic nomination, released a statement:

"I am glad to see Secretary Clinton is beginning to address an issue that my legislation addressed," Sanders said. "But her approach ignored the major issue. Secretary Clinton would classify marijuana in the same category as cocaine and continue to make marijuana a federally regulated substance."

"If we are serious about criminal justice reform and preventing many thousands of lives from being impacted because of criminal convictions for marijuana possession, we must remove marijuana from the federal Controlled Substances Act and allow states the right to go forward, if they choose, to legalize marijuana without federal legal impediments."

Last month, Sanders made an unprecedented move on marijuana. He became the first presidential candidate in history to support legislation that would federally legalize marijuana and remove it from the Controlled Substances Act entirely. He introduced a bill last week that would do just that.

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Sanders has always maintained that his support for marijuana legalization is based on his belief about the unfair penalization of non-violent drug users in the U.S. criminal justice system. Clinton, meanwhile, feels the country should continue to experiment with legalization at the state level and focus national efforts on medical marijuana.

"The problem with medical marijuana is there is a lot of anecdotal evidence about how well it works for certain conditions, but we haven't done any research," Clinton said at a campaign event Saturday. "Why? Because it is considered what is called a Schedule 1 drug and you can't even do research in it."

What Clinton said is somewhat misleading. Researchers around the world have demonstrated that marijuana effectively treats a range of health disorders, including chronic pain, epilepsy, and anxiety. But due to federal restrictions, American universities and research institutions have been largely barred from obtaining federal grants for marijuana research.

And while rescheduling marijuana as Schedule 2, as Clinton proposed, would be a step in the right direction, it means that the substance would remain federally illegal, stuck in the same drug category as cocaine and meth.

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"It may make research slightly easier, but on its own wouldn't do anything to protect seriously ill people who are using marijuana in accordance with state laws from being harassed by the DEA," Marijuana Majority chairman Tom Angell said. "Only changing the federal criminal statutes can effectively do that."