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How does the common law system work?

In order to understand how Canadian courts expand police powers, it is important to know how Canadian courts make law in the first place. 


Canada's legal system is a 'common law' system. This means that in addition to what is written in legislation, Canadian law comes from decisions made by courts. When an issue of law arises in a case (such as a question regarding what legislation means or the need to fill a gap in legislation arises) Canadian courts have the power to resolve these issues and clarify what the law is in a decision. This decision becomes 'binding precedent' which means that when similar legal issues arise in future cases, the previous decision must be adhered to. In other words, when similar police actions are challenged in court in the future, the court hearing that case must take guidance from the court's previous decision that allowed the police the specific power. Decisions from federal courts or the Supreme Court of Canada hold particular weight in this regard, meaning that lower courts are required to follow precedent set by higher courts. Decisions rendered by these higher courts are the ones that generally have the power to alter legal precedent. 

How are common law police powers expanded within the Canadian legal system?

Canadian courts expand ancillary common law police powers when an officer does something in the course of duty that is challenged in court and the court decides that conduct is within an officer's lawful power. A court applies a test established in R v Waterfield to make this determination. The Waterfield test first asks whether the police conduct in question was an unlawful interference with someone's liberty or property. If it was, then the court must ask whether (1) the conduct was in the scope of statutory or common law police powers and (2) whether the conduct was unjustifiable. 

Once this has been established in court, especially in a higher court, the ruling becomes precedent that can be followed by future courts. Our detailed look into the relevant case law shows how the Waterfield test has helped to expand common law police powers within the Canadian legal system. 


The House of Commons and provincial legislatures create laws that give powers to police to lawfully conduct their duties and obligations.


Courts such as the Supreme Court of Canada have the ability to create new common law police powers if there is a gap in the existing legislation.

expad in legal system

The Flowchart below provides a visual of how common law police powers expand with the application of the Waterfield test.

The actions of a police officer are brought to court on the basis that they interfered with the accused's liberty and/or property. 

The actions of the police officer pass the Waterfield test. 

The court therefore decides that the police conduct is a reasonable form of police work

Police may utilize this newly generated police power in the exercise of their duties.

All levels of the Canadian courts system can rely on the generated police power when considering future cases dealing with similar legal issues.


How does precedent help to expand common law police powers?

As we have discussed, once a court rules on an issue, it becomes precedent. In addition to this, the level of court impacts whether the precedent is binding on all jurisdictions or only the jurisdiction where the case was decided. Any ruling made by the Supreme Court of Canada is binding on the lower courts across the country. Precedents from a provincial court of appeal are binding at the trial level within that jurisdiction. However, other jurisdictions may find any decision dealing with police powers persuasive even if they are not jurisdictionally bound to follow the ruling:


The Supreme Court of Canada

The highest court in Canada. All lower courts must follow decisions made by the Supreme Court of Canada. The Supreme Court has the power to overturn any past legal ruling, including its own precedent.

Precedent flows down from the higher courts

Judge and Gavel

Court of Appeal

Each province and territory has an appeals court that reviews rulings at the trial level in its jurisdiction. Court of Appeal rulings are binding on the lower court in the jurisdiction it presides over and may be persuasive in other jurisdictions. These courts generally have the power to reverse/overturn past decisions under its jurisdiction that do not contradict Supreme Court rulings.

Trial Courts


Each province and territory has a Provincial Court and a Superior Court (sometimes called the Court of Queen's Bench) that presides over many different areas of the law. At the trial level:

  • all Supreme Court of Canada rulings must be followed

  • any appellate court ruling within its jurisdiction must be followed, as long as it is not contrary to a Supreme Court of Canada ruling

  • precedent at the trial level within the same jurisdiction must be followed, unless the ruling contradicts a Supreme Court or Court of Appeal ruling (within the same province)

  • any Provincial Court decision can be appealed to the Superior Court within the province

  • when there is no clear ruling on a legal issue at the appellate level, trial courts may find rulings in other jurisdictions persuasive in order to reach a decision.

A ruling within one province can be persuasive in another province.


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