A bill to set limits on driving while high faces a big test Monday in the Colorado Senate.
The bill, which aims to set limits on the amount of THCA a driver can have in their system when behind the wheel, has previously failed three times in the Senate.
States that allow medical marijuana have struggled for years to set definitive impairment levels. Unlike alcohol, marijuana stays in the blood long after the high wears off, and there's no quick test to determine someone's level of impairment.
The U.S. Supreme Court ruled recently that in some cases, officers will need a warrant in order to take blood from a someone suspected of being high.
This year's bill has cleared the House, but the hundreds of pot activists expected to be at the Capitol Monday hope that this year's version will once again fall short in the Senate.
Colorado and Washington have both been grappling with how to handle marijuana use ever since pot became legal last fall.