The Washington State Supreme Court on Thursday ruled that citizens can receive a driving under the influence charge for operating a motor vehicle while under the influence of cannabis, The Chronicle reports. The plaintiff, Douglas Fraser, argued that his 2017 DUI conviction was based on an arbitrary and vague standard for THC levels in the blood.

The unanimous decision upholds the state’s decade-old DUI law related to cannabis.

Justice G. Helen Whitener, in the opinion, defended the state’s law writing that while the “limit may not be perfect in terms of identifying the degree of impairment for all individuals, it is reasonably and substantially related to recent consumption, which is related to impairment.”

“The laws aim to deter people who have consumed cannabis from driving when there is a possibility they could be impaired, thus promoting some public interest of highway safety.” – Whitener, in the opinion, via The Chronicle

Fraser was arrested in 2017 after a State Patrol trooper witnessed him speeding, driving alone in the HOV lane, and driving dangerously. Fraser, who was wearing an employee badge from a cannabis dispensary, said he had last consumed cannabis “half a day” prior but that he was no longer impaired. After performing several field sobriety tests, the trooper arrested Fraser on suspicion of DUI. Subsequent tests found Fraser had a THC blood concentration of 9.4 nanograms per milliliter, with a margin of error of 2.5; the state’s limit is 5 nanograms per milliliter.

In court, Fraser argued that those limits are arbitrary and not tied to any evidence as a measure of impairment and included testimony from a physician who said the effects of THC can vary from person to person. The court rejected the argument, claiming that the limit serves its purpose by discouraging driving while stoned.