The possibility that the federal Liberals could strike down Canada's so-called "spanking law" came as joyful news to the woman who has spent more than two decades trying to dissolve the 123-year-old legislation.

"I was over the moon when I heard about this," Ailsa Watkinson told CBC News. "There's so much more evidence now to show the harm from childhood physical punishment."

And she knows the effect of it herself. Both she and her twin brother received "a brutal strapping" that the social work professor has never forgotten.

So in 1995, the University of Regina professor used her masters thesis to launch a charter challenge of Section 43 of the Criminal Code.

Court challenge

Six of the nine Supreme Court of Canada judges voted to uphold the law when the case reached them in 2004. 

But the ruling narrowed the scope of when parents can use "force by way of correction," laying out exactly what that punishment could look like. It also legally took away teachers' ability to use physical force, except to keep a student from harming themselves or someone else.

As the law stands now, parents cannot strike children with the intent to harm them, nor can they spank a child younger than two or older than 12.

Infants and toddlers could be physically hurt and likely would not see the connection between their actions and the spanking, while striking teenagers "can induce aggressive or antisocial behaviour," the 2004 Supreme Court of Canada ruling reads.

The judges also ruled that parents could not hit children with belts, rulers or other objects, nor slap them anywhere on the head.

Truth and Reconciliation Commission

Watkinson had renewed hope that law would soon be struck down after watching public and legal opinion change on physician-assisted suicide — and thanks to the recommendation of the Truth and Reconciliation Commission, which was adopted by the Liberal government..

It's unclear whether the law will be struck down or whether Ottawa plans to amend it.

"At this point, we cannot speculate on potential legislative or policy approaches to address this issue," Department of Justice spokesman Ian McLeod said in an email.

Watkinson said there's no need to replace the law, because other sections of the Criminal Code protect adults who step in to keep children from harming themselves or someone else. There's also the de minimis legal principle, which gives prosecutors the discretion not to proceed with charges in insignificant matters.

'The more often you're spanked, the fewer opportunities you have to learn a way of dealing with conflict that doesn't involve aggression.' - Prof. Joan Durrant

There's also mounting evidence to indicate that even mild forms of physical punishment — a slap or a light spanking — can have long-term effects on a child's emotional health and development, community health professor Joan Durrant said.

"Nobody is saying that if you're spanked, you're going to be violent," Durrant said. "But what it does mean is that the more often you're spanked the fewer opportunities you have to learn a way of dealing with conflict that doesn't involve aggression," she said.

"The more times a child is hit, the stronger that relationship becomes."

Nearly 50 countries have reflected that by abolishing physical punishment; Canadian law needs to do the same, clinical psychologists say.

Numerous studies have found that children will then try to solve their own problems by using violence throughout their lives, whether that's fighting with siblings, bullying or having a tendency to an increased chance of intimate violence, the University of Manitoba professor said.

Much of Durrant's research has focused on Sweden, which prohibited corporal punishment in 1979. She would like to see Canada follow that example — not simply to repeal the law, but to prohibit any sort of physical reprimand.

Protection for teachers

Teachers also fall under the protection of the spanking law, although they are not allowed to punish a child in any physical way, according to the 2004 Supreme Court ruling.

They can, however, step in if a child might hurt themselves, a teacher or a student.

And the president of the Canadian Teachers Federation said it's essential that any changes to Section 43 would include those same protections for education workers.

Without that, a teacher could theoretically face criminal charges for restraining a child who tries to run across the road or tries to strike another student, Heather Smith.

"We don't endorse corporal punishment, whatsoever," she said. "It's just physical intervention — and teachers use every tool in their toolbox before intervening physically."