Justice Clément Gascon of the Supreme Court of Canada just did something startling, and excellent. He wrote a dissent in Stewart v. Elk Valley Coal Corp. that drives some truck-size holes through a sloppy majority decision from Chief Justice McLachlin. Too bad he stands alone, but he certainly stands out. And his decision is a relief.

Stewart v. Elk Valley is a decision about drugs, safety and big machinery. This combination seems to seriously interfere with the reasoning capacities of adjudicators and judges. Gascon J. states at the beginning of his judgment: “I fully appreciate the safety-sensitive environment at the workplace of Elk Valley, and how that environment motivates strict drug policies for employees. Nevertheless, such policies, even if well-...