We hear a lot about the rule of law these days. The term is wielded by politicians like a judge's gavel — or a rhetorical cudgel.

Since the eruption of the SNC-Lavalin affair, Prime Minister Justin Trudeau's Liberal government has been accused by the Conservatives of not abiding by the rule of law. They've been further accused of interfering with the independence of the judiciary in the judicial selection process. The Liberals accused the Conservatives under Stephen Harper of much the same thing.

American politics has been in turmoil ever since the election of President Donald Trump, in no small part because of accusations that he flagrantly disregards the rule of law.

Most people would agree on some general principles of the rule of law — that no one is above the law, that governments and other authorities can't act arbitrarily and with impunity, and that fairness, justice, and equality before the law are pillars of our democracy.

But there's less agreement over who can credibly claim to be abiding by the rule of law. Often, people's perception of whether or not a political leader respects the rule of law seems to be a matter of where they sit on the political spectrum.

To get beyond the political rhetoric, The Sunday Edition's host Michael Enright interviewed University of Toronto law and philosophy professor David Dyzenhaus, one of Canada's foremost experts on the rule of law. They spoke what the term actually means, and when and where it's being violated.

Here is part of their conversation.

How would you define the rule of law?

Basically, the rule of law is the idea that goes back to Roman times that if we want officials to be in charge of our law, we also want that law to be in charge of the officials, so that they do not act arbitrarily in implementing the law.

Can you have a liberal democracy without the rule of law?

You can't have a democracy without the rule of law, because democracy is a set of institutions. They're legally constituted institutions, and without the rule of law one would not be able to avail oneself of those institutions. It's the rule of law that makes free and fair elections institutionally possible.

A case where the issue of the rule of law has come up recently is that of Huawei executive Meng Wanzhou, who was taken out of an airplane in Vancouver at the request of American Department of Justice officials to face extradition to the U.S. Both China and Canada claim to be following the rule of law themselves and accuse each other of not. How would you assess China's claim that indeed it's governed by the rule of law?

I don't think China has any basis for claiming that it's ruled by the rule of law. I was just in Hong Kong doing some work at the Hong Kong University, and constitutional law scholars explained the mainland Chinese legal order to me in the following way — that when it comes to private law and private law transactions, one does have something like the rule of law. There's contract law and in a contractual dispute you can go to a court and get a ruling.

The U.S. is seeking the extradition of Huawei chief financial officer Meng Wanzhou, but Canada appears to be bearing the brunt of China's displeasure. (Darryl Dyck/The Canadian Press)

But when it comes to any matter that concerns the Communist Party, there the say-so of a Communist Party official is what will determine your fate. If you have that kind of system in place, you do not have the rule of law.

What happens if the rule of law is in conflict with political traditions and customs — the rights of emperors and kings and all that?

The rule of law was something that was put in place in order to curb the right of kings to do as they please. To put the rule of law in place meant that those who wished it to be in place had to struggle against a political culture that was hostile to the rule of law.

So in other words, then, it would be impossible to have the rule of law in a dictatorship or an authoritarian regime.

The rule of law in a dictatorship or an authoritarian regime is, at least, put under huge strain. To the extent that one has the rule of law, the regime will be less authoritarian or less dictatorial can you have laws that contravene the rule of law.

Let's look at the United States following the Civil War. There were a whole series of laws called the Jim Crow laws, and there was a series of high court decisions like Plessy v. Ferguson. Can a country with flagrantly unjust and discriminatory laws be said to be following the rule of law?

That's an example of law being used to discriminate against large groups of people, and of course, it's the case that law has been used in this way and will be used in this way. There's no escaping that.

I think it's interesting when one looks back at the history of racism in the United States of America. Or the history of slavery in that country, or at apartheid South Africa. It's interesting to reflect on the lessons that we can learn for our contemporary societies, because it would be a grave mistake to suppose that in Canada, for example, law is never used to perpetuate injustice.

A quite recent example which came out of the issues that arose in regard to SNC-Lavalin is when the former attorney general was asked to move to a different portfolio — to Indigenous affairs. She refused, apparently on the basis that she would be asked to oversee the implementation of a statute that she regarded as illegitimate — the Indian Act. And certainly Indigenous groups in Canada do not regard the statute as an instrument of justice, but as an instrument of injustice.

“We either have a system that is based on the rule of law, the independence of prosecutorial functions and respect for those charged to use their discretion and powers in a particular way, or we do not.” 0:52

Well, what does that suggest about the strength of the rule of law in Canada?

I think that Canada is one of the most rule-of-law-abiding countries that I know, and what it suggests is that the fact that there is an unjust law in place creates problems within the rule of law for Canadians. They have to ask whether their society is living up to its most fundamental legal commitments.

Our constitution says that the country is founded on principles that recognize the sovereignty of God and the rule of law.

I think that phrase about God in the preamble to the Constitution is not a phrase that has any legal bite to it. The important term, legally speaking there, is the rule of law.

To follow the sovereignty of God, which might mean following any interpretation of God's will that a particular person held to, would be the end of the rule of law.

One of the issues that you have written about is the way Canada appointed judges especially to the Supreme Court.

For many years, that appointment process has worked very well, and judges have enjoyed a reputation for independence and impartiality. I think during the last years of Stephen Harper's reign in Canada, that reputation was somewhat tarnished. It did become clear at a certain point that lawyers who wished to be appointed as judges need not apply if they did not belong to a certain part of the political spectrum. If one appoints judges only from one part of the political spectrum, then it starts to look as if one wants to have judges in place that are going to do the bidding of the government, rather than judges who will be committed to the rule of law.

Stephen Harper faced criticism for the way he appointed judges to Canada's top court. (Adrian Wyld/Canadian Press)

When you were mentioning President Trump, and how on several levels he seems to be flouting the rule of law … how dangerous is it for the whole concept of the rule of law internationally, when it's being eroded in the United States?

It's hugely dangerous. The United States regards itself and is regarded as one of the leaders of democracy — a country in which there has been the rule of law for centuries, however tarnished it has been by slavery and racism.

If it becomes the case that the leader of their country shows utter disregard for the rule of law, and worse, his disregard for the rule of law is camouflaged by judges who will uphold his actions as legal even if they are illegal, then I think the rule of law is in real trouble.

To hear the full interview, click 'listen' above.

Q&A has been edited for length and clarity.