Celebrated author Mark Steyn has been summoned to appear before two Canadian judicial panels on charges linked to his book “America Alone.”

The book, a No. 1 bestseller in Canada, argues that Western nations are succumbing to an Islamist imperialist threat. The fact that charges based on it are proceeding apace proves his point.

Steyn, who won the 2006 Eric Breindel Journalism Award (co-sponsored by The Post and its parent, News Corp), writes for dozens of publications on several continents. After the Canadian general-interest magazine Maclean’s reprinted a chapter from the book, five Muslim law-school students, acting through the auspices of the Canadian Islamic Congress, demanded that the magazine be punished for spreading “hatred and contempt” for Muslims.

The plaintiffs allege that Maclean’s advocated, among other things, the notion that Islamic culture is incompatible with Canada’s liberalized, Western civilization. They insist such a notion is untrue and, in effect, want opinions like that banned from publication.

Two separate panels, the British Columbia Human Rights Tribunal and the Canadian Human Rights Commission, have agreed to hear the case. These bodies are empowered to hear and rule on cases of purported “hate speech.”

Of course, a ban on opinions – even disagreeable ones – is the very antithesis of the Western tradition of free speech and freedom of the press.

Indeed, this whole process of dragging Steyn and the magazine before two separate human-rights bodies for the “crime” of expressing an opinion is a good illustration of precisely what he was talking about.

If Maclean’s, Canada’s top-selling magazine, is found “guilty,” it could face financial or other penalties. And the affair could have a devastating impact on opinion journalism in Canada generally.

As it happens, Canadian human-rights commissions have already come down hard on those whose writings they dislike, like critics of gay rights.

Nor should Americans dismiss this campaign against Steyn and Maclean’s as merely another Canadian eccentricity. Speech cops in America, too, are forever attempting similar efforts – most visibly, on college campuses.

In fact, New York City itself has a human-rights panel that tries to stamp out anything deemed too politically incorrect.

Since 9/11, Americans have been alert to the threat of terror from radical Islamists. But there’s been all too little concern for a creeping accommodation of radical Islamist tenets, like curbs on critical opinions.

That needs to change.