JUNEAU, Alaska (AP) — An Alaska marijuana retailer’s tax payment has been sent back to the business after the U.S. Postal Service refused to ship the money.

Rainforest Farms had recently tried to send a box full of cash to pay its taxes, but postal inspector Aaron Behnen said “any proceeds from the selling of (marijuana) is considered drug proceeds under federal law, so you can’t mail that,” the Juneau Empire reported Wednesday.

Ken Alper, Alaska’s tax director, said the state needs to find a way for “these legitimate businesspeople to pay their taxes.”

“We thought we had done that, and this throws a tremendous wrinkle into our processes,” he said.

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Rainforest Farms had been trying to send its tax money to Anchorage. And since banks have locked out the marijuana industry in fear of federal laws, the farm sent its payment in the form of a box full of cash.

“It’s difficult. People like cash, but it does take a lot to move it, especially when you have to account for it properly,” said James Barrett, one of the owners of Rainforest Farms.

Being locked out of banks, and marijuana being illegal federally, makes running the business a challenge, Barrett said. Mostly all dealings are in cash, he said.

State Rep. Don Young has created a Congressional Cannabis Caucus with fellow representatives to work on getting a bill passed to protect banks and credit unions that choose to service marijuana-related businesses.