DENVER — When asked, the people who know hemp the best say it’s an industry that’s only going to get bigger. Those same people also say its long-been in the shadows of a legal gray area, and the confusion about what’s allowed and what’s not is still there, despite it being legalized under federal law.

President Donald Trump signed the 2018 Farm Bill into law in December, classifying hemp as an agricultural commodity. Before, individual states had different rules on the books, some completely banning hemp and others allowing pilot projects, like in Colorado.

That’s where some of the confusion starts.

“Federal law passed and legalized hemp, but that didn’t change the laws in the 50 states for hemp," said David Wunderlich, who specializes in hemp law.

Wunderlich works with different companies involved in hemp, including ones that move it across state lines. The 2018 Farm Bill allows that.

However, on Jan. 9, four people on their way to Colorado were stopped in Pawhuska, Okla. for allegedly running a red light. The two men in charge of the shipment's security insisted they were legally transporting hemp. The officers insisted they were transporting marijuana and arrested them, along with the two drivers for drug trafficking.

RELATED: Hemp or marijuana? After drug test, future of Aurora man accused in drug trafficking case remains uncertain

RELATED: Government shutdown delays drug test in marijuana trafficking case

RELATED: Aurora man among 4 people accused of trafficking massive pot shipment (but police aren't sure it's pot)

In a separate case in Idaho, a company has filed a lawsuit against local authorities for seizing what they say is hemp, as well - also on its way to Colorado. 9NEWS' sister station KTVB reports that truck was carrying 7,000 pounds of either hemp or marijuana.

Wunderlich said because of the conflict in law, both before and after the 2018 Farm Bill, he advises his clients to make sure they have their paperwork in order - that includes the license for the company that grew the hemp and the tests that show what they are carrying has 0.3 percent or less of THC, which is the federal legal limit for hemp.

Colorado’s pilot project allows hemp to be grown for research and commercial purposes. Justin Henderson grows hemp in the Denver area and doesn’t pass the buck when it comes to knowing the law.

“It’s the person or company’s obligation to know the law, not the state’s obligation to educate. That keeps us on our toes," said Henderson.

Henderson said the 2018 Farm Bill doesn’t impact his operations day to day, since he doesn’t export outside Colorado, but he did say it’s concerning to see the confusion over transportation and arrests.

“I think it allowed to open some dialogue,” he said. “I think there is some room to go.”

Even though hemp is grown in Colorado, some companies choose to import hemp from other states because there was a bottleneck in production last year, according to both Wunderlich and Henderson. Both said it’s expected to clear out this year as more hemp labs open. Of course, some companies may choose to import hemp because of cost, and if an outside product has certain qualities they are looking for.

Under the 2018 Farm Bill, Wunderlich said states have a year to figure out a hemp plan. If they don’t, the feds come up with one for them.

He also said states have the ability to come up with rules that are stronger than federal law out of concern for the safety and health of a community, which could include criminal law and defining something as a controlled substance that is not controlled in other states or by the federal government.

More from Next with Kyle Clark