EXCLUSIVE

A Nevada state senator is coming out swinging in defense of UFC superstar Nick Diaz -- claiming his 5 year ban for weed is a complete load of crap.

TMZ Sports spoke with Senator Tick Segerblom of Senate District 3 -- which includes parts of Las Vegas -- who says he's not happy with the punishment doled out by the Nevada State Athletic Commission.

"I think what they did was totally inappropriate," Tick says ... "[marijuana] is a recognized medicine in the Nevada constitution so how can you punish someone for taking medicine, particularly since it doesn’t enhance your ability to fight?"

He added, "They need to rethink this punishment and then ultimately change their rules."

FYI -- Diaz tested positive for weed after his UFC 183 fight in January.