Colorado lawmakers on Tuesday rejected a bill that would have set a legal blood-level limit for the active ingredient in marijuana, THC. Currently convictions for drugged driving in the state depend on an officer’s observations, according to the Associated Press.

It is the third time Colorado’s legislators have rejected a measure to set a legal limit for THC, the AP reports. The House passed the bill, which would limit drivers to 5 nanograms of THC per milliliter of blood. The state Senate vote was tied, failing to pass by one vote. An amendment to exempt state-certified medical marijuana patients from the limit failed.

Some of the bill’s critics said more than 90 percent of the state’s drugged-driving criminal cases end in convictions, and argued that instituting the legal limit would be unlikely to change behavior. Others said the measure should have targeted more than just marijuana.

More than a dozen states have a zero-tolerance policy for driving with any presence of an illegal substance, the article notes.
Nevada and Ohio have a 2 nanogram THC limit for driving. In Washington state, voters will consider a 5 nanogram THC driving limit, as part of a ballot measure about marijuana legalization in November.

The White House Office of National Drug Control Policy has asked all states to adopt drugged driving laws that set blood limits, but has not told states what nanogram limit to set for illegal drugs.