Marijuana is such a confounding drug that scientists and law enforcement are struggling to create an objective standard for marijuana intoxication.

IF YOU’VE SPENT time with marijuana—any time at all, really—you know that the high can be rather unpredictable. It depends on the strain, its level of THC and hundreds of other compounds, and the interaction between all these elements. Oh, and how much you ate that day. And how you took the cannabis. And the position of the North Star at the moment of ingestion.