A Billings, Montana man charged with vehicular homicide while under the influence of marijuana is challenging the state standard at which a person is considered to be under the influence.

Public defender Gregory Paskell says the THC blood level set by the state is arbitrary, and he’s asking that the charge against Kent Roderick Jensen be dismissed.

Jensen, 20, is charged in the 2016 death of motorcyclist Jashua Fry, The Billings Gazette reports. Court records say Jensen pulled out onto a road without seeing the motorcycle, causing the fatal crash.

Jensen’s blood contained 19 nanograms per milliliter of THC, the active ingredient in marijuana, court records said. State law says a person is under the influence with a blood level of 5 ng/mL of THC.

“There is no science to back up the 5 ng/mL level as a level that indicates impairment in a sizable enough portion of users to make it a standard for everyone,” Paskell wrote.

Montana is one of 18 states with marijuana-specific impaired driving laws, according to the Governors Highway Safety Association. A dozen states have zero tolerance for marijuana or its metabolites.