Senator Warren, a Democrat of Massachusetts, is in the headlines for joining with Senator Cory Gardner, a Republican who represents Colorado, to introduce the Strengthening the Tenth Amendment Through Entrusting States Act. That legislation would, as Warren put it in a tweet, “let states, territories, & tribes decide for themselves how best to regulate marijuana — without federal interference.” Justice Thomas is Warren’s natural ally on the issue. He wrote an emphatic dissent in the 2005 Supreme Court case Gonzalez v. Raich. Alberto Gonzalez was President George W. Bush’s attorney general, and Angel Raich is an Oakland, Calif., woman who...