Maybe- maybe not.
Under the circumstances you should do a great deal of research on this before attempting to purchase a firearm. To my knowledge in order for Joshua's parents to purchase CBD oil requires them to obtain an MMJ (medical marijuana) card in accordance with South Carolina law.
However having such a card in your name may prevent you from even possessing a firearm under federal law based on the outcome of a decision appealed in Nevada (Wilson v. Lynch) and upheld up by the Ninth Circuit Court of Appeals:
"The case was filed by a woman denied a firearms purchase because the firearms dealer knew that she held a medical marijuana card.
https://www.cannalawblog.com/wilson...-guns-and-medical-marijuana-dont-legally-mix/
The 9th Circuit is notoriously unfriendly to gun rights, so it is not surprising that they issued the opinion they did, but coupled with the Drug Enforcement Administration's refusal last month to reclassify marijuana as a Schedule II drug, it is a devastating blow to Second Amendment rights and marijuana activists regardless."
"If you think that you can purchase firearms and then get an MMJ card and be in the clear, I wouldn't be so sure.
The ATF is not known to err on the side of the individual in gray areas, and it has made it very clear in the above "Open Letter" that possession of both firearms and MMJ cards is going to be a problem.
All the ATF has to do is feed the list of MMJ cardholders into the NICS background check database, and the result will be a denial. "
9th Circuit Affirms Catch-22 for Gun Owners, MMJ Users
In the meantime there is legislation pending in the House of Representatives through the office of Rep. Thomas Massie (KY) to delete the question of marijuana use from the ATF form 4473 altogether. Of course like all pending legislation, there's no guarantee it will pass to the Senate or be signed into law by the president.
Lawmaker drafting bill to remove marijuana question from ATF gun form