Sometime around Memorial Day, the TSA changed its stance on carrying onboard a plane a medication that treats childhood epilepsy and on CBD oil, which WebMD calls “the hot new product in states that have legalized medical marijuana.” CBD oil is said to relieve pain.

It also does not get you high, according to Harvard Medical School’s Healthbeat newsletter.

Under TSA’s “What Can I Bring” program that lets passengers ask about items that may or may not be allowed on planes, its previous advice on medical marijuana, including CBD oil, was no and no for carry-on bags and checked bags.

But if you look at the page today, it says medical marijuana can be transported in carry-on bags and checked bags, with the proviso of “special instructions.”

“Products/medications that contain hemp- derived CBD or are approved by the FDA are legal as long as it is produced within the regulations defined by the law under the Agriculture Improvement Act 2018.”

Quickly, travelers, does your CBD oil conform with that law? And, more to the point, how will TSA officers be able to recognize what does or does not adhere to the new law?

Answer to the first question: The CBD oil you have today probably does not conform to that law.

Answer to the second question: TSA officers probably couldn’t differentiate, but the point may be moot, one policy expert said.

When TSA was asked about these questions, it was still consulting its attorneys for answers.

What we can say for sure: It’s messy.

As Hawaii residents know, marijuana, for medical use, is legal in this state and several others.

Although you may be free to use cannabis products in your home state, the use and possession of such products is illegal under federal law.

But TSA’s own page is a kind of a wink and a nod to carrying such products: “TSA’s screening procedures are focused on security and are designed to detect potential threats to aviation and passengers,” it says. “Accordingly, TSA security officers do not search for marijuana or other illegal drugs, but if any illegal substance is discovered during security screening, TSA will refer the matter to a law enforcement officer.”

The strictest interpretation of the law, until recently, has been no, you can’t have it in your carry-on or checked bag. But the change in policy seems to walk that back, “seems” being the operative word.

Here is what we know for sure: Epidiolex, a drug used for treating epilepsy in children, is permitted in carry-on and checked luggage. The Food and Drug Administration approved it in June 2018. “This is the first FDA-approved drug that contains a purified drug substance derived from marijuana,” its announcement said.

Then TSA had to act. “TSA was made aware of an FDA-approved drug that contains CBD oil for children who experience seizures from pediatric epilepsy,” the TSA said in a recent statement. “To avoid confusion as to whether families can travel with this drug, TSA immediately updated TSA.gov once we became aware of the issue.”

For clarity on the Agriculture Improvement Act 2018, I turned to John Hudak, a senior fellow at the Brookings Institution, a public policy organization, and author of “Marijuana: A Short History.”

In a Dec. 14 piece on Brookings’ website, he explained more about the farm bill:

Here’s the first roadblock to CBD, which generally derives from hemp: “Hemp cannot contain more than 0.3% THC, per section 10113 of the farm bill,” Hudak’s post said. “Any cannabis plant that contains more than 0.3% THC would be considered non-hemp cannabis — or marijuana — under federal law and would thus face no legal protection under this new legislation.”

THC is what creates the high, but how can an officer know how much THC is in any substance? He or she cannot, in all likelihood.

But that may not matter, Hudak said, because of Part 2 of this conundrum: States’ plans for the production of hemp must be approved at the federal level. Thus there is no CBD at the moment that meets the requirements of the law.

How this ultimately may be solved, from an enforcement perspective, may include packaging that indicates legality, Hudak said.

But until then, be aware that you walk a fine line in the regulation/enforcement of CBD through TSA. Proceed with caution.