The very short answer to the question "Is CBD oil legal in South Dakota?" is—nope. Marijuana is still considered illegal, and cannabidiol (CBD) products have a Schedule IV drug status in the state. In 2017, state law was amended to allow CBD products that were approved by the FDA, only one of which has been given this status so far. (This year, the CBD drug was approved with an indication for the treatment of serious epilepsy conditions. It can only be doctor-prescribed.)
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For this reason, law enforcement across the Mount Rushmore State continues to crack down on CBD product suppliers. However, the state vs. federal law remains confusing for residents and business owners, because not only is the Farm Bill 2018 up for review (and is poised to give legal status to all hemp-derived CBD, if passed), but the national law has already explained its status.
In June, the Drug Enforcement Administration (DEA) clarified a new drug code, explaining that CBD derived from certain parts of the hemp variety of theCannabis sativa L. plant is considered legal. 
CBD is the non-intoxicating or non-psychotropic compound found in cannabis.
Talking to theRapid City Journal, Rapid City store owner Leonard Vandermate said about the law, after his shop was raided by the police:
“There’s such a gray area. Half the people says it’s OK. The other half says no. Some say yes. Does state law trump federal? Or the other way around? It’s just confusing.”
He also noted that his customers were very unhappy. One of them is a woman with stage 4 breast cancer, who had an informal referral from a Mayo Clinic doctor to purchase CBD products from Vandermate’s store.
Vandermate said: “These people are going to go back to abusing alcohol or opioids or the crap we’re trying to get rid of to deal with this pain.” 
So, it seems that if you are very sure where your CBD is sourced from, and you're up to confronting and educating the local law forces, you should be reasonably protected.
Having state-mandated marijuana available for medical purposes doesn't seem to be high on South Dakotans' priority list, or something else is going on. The so-called South Dakota Medical Marijuana Initiative was not on the ballot as an initiated state statute in November this year. Apparently, this was due to the fact that the initiative fell short of the signature requirement by 4,401 valid signatures.
According to Ballotpedia, signature requirements in South Dakota are based on the total number of votes cast in the state's most recent gubernatorial election. A number of signatures equal to five percent of this total was necessary for qualifying initiatives for the 2018 ballot.
Perhaps this year's strict law enforcement action will galvanize more constituents to sign and participate more vocally in the state's lawmaking process, so the ballot can pass. This will start the process to make medical marijuana legal in the state for the following debilitating conditions:
(Verbatim from the Ballotpedia site)
A chronic or medical condition that produces any of the following symptoms would also have been considered a debilitating medical condition:
The proposed act is well thought-through and will make provision for three grams of legal medical marijuana per person. That, or the cultivation of six cannabis plants minimum, or as prescribed by a qualified physician. 
As stated, cultivating, selling, or possessing marijuana are all outlawed in South Dakota.
Possession of up to two ounces of marijuana will count as a misdemeanor if you get caught. More than that is subject to felony-based penalties on a scale, depending on the amount. This includes all forms of hashish.
If you get caught selling more than half an ounce of marijuana, it’s a felony, with a mandatory 30-day sentence. If it's found in your vehicle, your license is suspended for 90 days if it's the first offense.
Cultivation of marijuana will be punished based upon the aggregate weight of the plants found as either simple possession or as possession with the intent to distribute, according to FindLaw.
They also point out that out-of-state medical prescriptions are not recognized in the state and will not provide any defense to marijuana possession.
Under federal law, sale and cultivation of marijuana carry even heavier penalties—a first offense could land you in jail for five years, depending on how much you get caught with. A large amount can see you sit in jail for life, with a million-dollar fine. 
So, it is clear, CBD oil is not legal in the Rushmore State, and South Dakota marijuana laws are pretty strict. There also seems to be no change on the horizon soon, as evidenced by shops that get raided of CBD products even after the national law has changed in this regard. Many people still feel it worth the risk, because they really need CBD oil and related products for health purposes.Thankfully, hemp-derived CBD is readily available and is 100% legal in all US states. It is used by many for ailments as diverse as severe insomnia to HIV and cancer. In this instance, it would probably be best to order from a reputable shop online.
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