I suspect there are going to be some very busy defence lawyers,prosecutors,judges and labour experts trying to figure out what impairment actually is.
We—as a society have accepted that .08 millilitres of alcohol in 100 millilitres of blood constitutes impaired driving—as determined by a breathalyzer. It’s not so easy with Cannabis.
I remember when the first breathalyzer came out. The results from those things weren’t universally accepted—that took years of studies—educating the public and literally thousands of cases before the courts.
In this locality throughout the 1970’s drink and driving was tolerated—even by the police. Up until about 1980 the only drunk driving charges I heard about involved an accident.
People are nowadays more aware and the penalties are very severe but there are no doubt going to be some bad actors.