I'm not an expert just SGOTI and the following is what I have figured out recently when I was made curious from the other thread. So it's worth what you paid for it.
Various bills at the Federal level recognize the difference between "industrial hemp" and "marijuana". It's the same basic plant but the former has been bred to contain almost no THC. (<0.3% by dry weight) Industrial hemp has been legalized by the Federal government to grow in some areas for research and other purposes. There is a strong bipartisan effort to fully legalize industrial hemp across the board to boost farm economies, to replace tobacco as a crop, and create domestic and export markets for hemp products like fabrics, rope, soap, lamp oil, etc.
The DEA has obstructed these efforts. (What seems to be going on is the pharmaceutical lobbiests want to have CBD declared a drug by the FDA so they can control its production and marketing and the DEA is kindly helping them by declaring CBD in addition to THC a schedule 1 substance.) It's an ongoing battle at this point with several court cases, the Federal government in the meantime does not seem to be prosecuting the sale and use of CBD, especially if hemp derived, but I would not take that to mean the FAA is okay with it. I would stay away from all forms of CBD from the standpoint of medical certification with the FAA.
There are different types of "CBD" products:
1.) Hemp oil: Made from industrial hemp. It contains no THC and no CBD but could be marketed as "CBD oil" and if so is a rip off. It can be used as a cooking oil but does not have medicinal benefits. What you see on Amazon.com as "Cannabis Hemp Oil" is this. It's completely legal just like it's legal to own a garment made from hemp.
2.) Hemp derived CBD oil: Also made from industrial hemp, but does contain varying amounts of CBD which is considered to have immune system benefits or other health benefits but doesn't get you high.
3.) Marijuana derived CBD oil without THC: Made from the parts of the marijuana plant that do not contain much if any THC. This oil may or may not contain much CBD. It is technically still illegal in most states because it came from the marijuana plant.
4.) Marijuana derived CBD oil with THC: Made from marijuana, contains THC and is definitely disqualifying as far as the FAA is concerned even if you get it with a legal prescription.
Personally I'd stay away from all of them. Even the first because I would not trust sources to not contaminate it with THC.