From romantic comedies showing otherwise responsible adults taking a hit off of a joint at dinner parties to stories of "green doctors" handing out medical marijuana cards with a wink and a nod, it can sometimes seem like the battle of public opinion over marijuana is long over. Yet the drug remains illegal in the United States. 

Jesse Ventura, the former Independent governor of Minnesota and the author of "Jesse Ventura's Marijuana Manifesto," thinks he knows the reason why. Ventura penned an editorial for CNBC, released Thursday, alleging that due to a myriad of conflicts of interest, the U.S. Drug Enforcement Agency (DEA) will never legalize marijuana, regardless of public opinion. 

"Last week, the DEA decided not to reschedule the classification of marijuana as a legal drug," Ventura wrote. "According to federal drug codes, cannabis is still as deadly and addictive as heroin, with no known medical value. I was surprised to see how many articles were written about this decision without mentioning the obvious: This was going to happen. The DEA was just toying with us."

Ventura, a longtime advocate for marijuana legalization, says that because the DEA oversees the approval of research on the medical effects of marijuana in the U.S., they have the ability to hamstring the flow of information to the public and preserve the profitable industry of enforcing marijuana laws. 

"The DEA is in charge of approving scientific research studies! Now, the DEA isn't an independent organization or a scientific organization — they are a law-enforcement organization — yet they are given the responsibility to be both judge and jury when it comes to what research studies can be done within the United States?" Ventura continued. 

Jesse Ventura Former Minnesota Gov. Jesse Ventura says the DEA has "toyed with" the American public on the issue of legalizing marijuana. Photo: Getty Images

Last week, the U.S. government announced that it will allow significantly more research into marijuana, upping the number of research universities in the country that are authorized to study the drug. However, that announcement was coupled with the news that the DEA will not remove marijuana's classification as a Schedule 1 drug, a distinction legalization advocates have been eager to see changed. The Schedule 1 designation keeps marijuana illegal under federal law and classifies the drug as dangerous and highly addictive with no medical use, putting it legally in the same category as heroin. 

Following the news that the DEA would not reschedule marijuana, legalization supporters began posting pictures of their hands holding the drug with the number "6,630,507" written on their palms. The viral campaign was intended to point out the hypocrisy of marijuana being federally illegal despite the fact that the U.S. Department of Health and Human Services has held a patent on the drug since 1999. Critics argue that if the government can possess and study the drug for its medical effects, it is not fair that for regular citizens that marijuana falls into the Schedule 1 category, deeming it of no medical value. 

See where the 2016 presidential candidates stand on marijuana legalization HERE