The Liberals have introduced Bill C-9, their latest attempt to police so-called "hate speech." The mischief runs so deep, and through so many channels, that one hardly knows where to begin the excavation. Best, then, to return to first principles. For it is there, deep in the bedrock of our Canadian legal inheritance, that Bill C-9 reveals itself as a rupture with centuries of jurisprudential wisdom.

Bill C-9 creates a new definition of hatred as involving "detestation or vilification". Since when are emotions crimes? As for vilification — harsh or damaging speech — that has long been addressed by defamation law. One suspects the answer lies not in legal necessity but in a desire to regulate opinion under the guise of regulating harm.

For a millennium, the Common Law has held that malevolence must hitch itself to a prohibited act before the state may intervene. Words alone, however offensive, have not sufficed. The wisdom in this distinction becomes clear when we consider the fate of controversial speakers.

In 1968, Enoch Powell delivered his notorious "Rivers of Blood" speech. Reviled in Parliament and the press, dismissed from the Shadow Cabinet, condemned across the political spectrum — Powell nonetheless committed no crime under English law. His remarks were inflammatory, perhaps reckless, but they did not incite violence or direct harm. The social value of protecting free expression outweighed the offence he caused.

Could Powell speak today? Under Bill C-9, his speech would almost certainly constitute the "wilful promotion of hatred." No act would be needed. Words, transmitted through any medium, would suffice. The actus reus evaporates; the crime consists in the expression of a disfavoured thought.

Bill C-9 represents an attack on the very structure of the Common Law, that hard-won system designed to restrain arbitrary power. The Common Law has always recognized that criminal law is the state's harshest tool and must be used sparingly. It has understood that thoughts, however loathsome, are not crimes. It has insisted that the boundary between regulating conduct and policing belief must be zealously guarded.

When the state criminalizes thoughts rather than deeds — when prosecutors may infer criminality from mere expression — we abandon the principles that have protected liberty since Magna Carta. We trade the sturdy protections of actus reus and mens rea for the soft authoritarianism of enforced social harmony.