The roughly 2,500 medical marijuana dispensaries in the United States pay taxes to local, state and federal governments.

But they can’t take the same federal tax breaks that other small businesses take.

A section of the federal tax code known as 280E was meant to prevent tax write-offs for illegal drug activity. It was enacted in 1982, before medical marijuana was legalized in any state.

Now the Internal Revenue Service is applying 280E to pot shops operating legally under state law.

Read more: Medical marijuana stores blocked from federal tax breaks | USA Today