The law says it is wrong for a man to hit a woman, but okay for a parent to hit a child.

A man who strikes a woman in a family dispute meets zero tolerance from police, but a parent who strikes a child for misbehaving is seen as acting properly.

Some people say that's crazy. If Canadian law protects women from assault of any kind, why does it deny the same protection to children, who are smaller and more vulnerable? The reason, other people say, is that hitting a wife in anger is a lot different from spanking a child.

"I think the overall problem about this issue is that it is such a deeply personal one," says Peter Newell, co-ordinator of global lobby group End Physical Punishment of Children, based in London, England. "Most people were hit as children," he said by phone recently. "Most parents have also hit their own children. That makes it difficult for people to come to a logical conclusion — that children and adults be protected equally."

On Friday, the Supreme Court of Canada is to rule on the question. Specifically, the court is to decide whether to abolish Section 43 of the Criminal Code, which offers parents and schoolteachers legal justification for physically disciplining a child.

A Toronto group called the Foundation for Children, Youth and the Law argued in June that the statute violates a child's constitutional rights, including rights to equality and security of person.

In response, federal lawyers agreed that spanking is bad parenting — "It's never okay to spank children" — but said that Section 43 rightly upholds a parent's authority to raise a child without undue government interference. It would be absurd, government lawyers said, to expose parents to the threat of criminal prosecution "for every trivial slap or spanking."

So far, 12 countries — mostly in Europe — have changed laws to prohibit parents from striking their children.

In October, a United Nations committee ruled that Canadian law violates the U.N. Convention on the Rights of the Child, and that Canada should "prohibit all forms of violence against children, however light." The committee specifically called for abolishing Section 43.

But if the Supreme Court does strike down the section, a lot of parents are in for a surprise. Spanking would be no different in law from any other common assault, a criminal act punishable by imprisonment for up to five years.

In Canadian law, any unwelcome touch is considered assault. Any unwelcome force by one person against another, no matter how mild, is illegal.

Historically, various exemptions have applied.

Under English common law, masters could once legally strike servants and husbands could, in moderation, beat their wives. After the codification of Canadian criminal law in 1892, employers could still legally hit apprentices, and prison wardens were justified in flogging inmates with a cat-o'-nine-tails.

Only two exceptions still remain. The law continues to offer a legal defence to ship commanders who use force against sailors to maintain order. Similarly, Section 43 of the Criminal Code offers a defence to parents and schoolteachers who hit a child, provided that the purpose is to correct the child's behaviour and that "reasonable" force is used.

The full text states: "Every schoolteacher, parent or person standing in the place of a parent is justified in using force by way of correction toward a pupil or child, as the case may be, who is under his care, if the force does not exceed what is reasonable under the circumstances."

Critics view Section 43 as a relic from another age. "Culturally anachronistic and historically outdated," Italy's top court called a similar Italian statute in 1996, when declaring all physical punishment of children in Italy illegal.

The word "reasonable" draws particular criticism. Even lower-court judges have complained of loose wording.

In a 1996 child assault case, Mr. Justice Ian MacDonnell of the Ontario Court of Justice (provincial division) complained of "the elusive nature of the standard of reasonableness." Two years later, Mr. Justice Brian Weagant of the same court cited "the wide variety of judicial interpretations" of Section 43, and said the law "begs for legislative reform."

Anne McGillivray, a law professor at the University of Manitoba, said in a telephone interview that the vagueness makes Section 43 "a legal lottery." The interpretation of "reasonable under the circumstances" is subject to what she called "the judicial childhood test," meaning subject to a judge's own childhood experience.

McGillivray cited the case of an 8-year-old Winnipeg boy who opened a pack of sunflower seeds after his father told him not to. The father kicked the boy several times and hit him across the shoulders, leaving a mark. The father was convicted of assault causing bodily harm and sentenced to anger management counselling. He appealed to the Manitoba Court of Appeal and, in 1994, was acquitted.

"The discipline administered to the boy in question in these proceedings," said the appeal judge, "was mild indeed compared to the discipline I received in my home. There were times when I thought my parents were too strict, but in retrospect I am glad that my parents were not subjected to prosecution or persecution for attempting to keep the children in my family in line."

Because of the ruling, McGillivray said, fewer child-abuse cases are coming to court in Manitoba. To get a conviction, prosecutors know they must prove that parental force was more severe than punching and kicking.

Similarly, the Toronto-based Repeal 43 Committee, the country's foremost lobby group on the issue, says parents are successfully invoking Section 43 as a defence for child abuse. The committee compiled a list of 22 such precedents set between 1990-2001.

In Newfoundland two years ago, a father who struck his 14-year-old daughter with a belt, leaving welts and bruises on her legs, was acquitted under Section 43. In Ontario two years ago, a father who struck his 11-year-old son with a belt leaving a buckle-shaped mark on his thigh was similarly acquitted.

In Saskatchewan in 1987, in a case McGillivray cited, a man and a woman who stripped their two nieces, 13 and 14, to their underwear, tied their hands to a basement clothesline and strapped them across their buttocks, were judged to be carrying out "corrective" and "reasonable" punishment.

"We see (Section 43) used (in cases where) parents not merely spank their children, they use weapons," Paul Schabas, lawyer for the Foundation for Children, Youth and the Law, told the Supreme Court judges. "They use implements on children. They cause injury. They strip children and hurt them."

Apart from the vagueness of "reasonable," children's advocates said in interviews, the law wrongly puts its seal of approval on spanking.

"Parents interpret Section 43 not as a defence against assault but as a general permission to use force against children," said Alfred Mamo, lawyer for the Children's Aid Society in the high-profile Church of God case, in which seven children were found to be in need of protection last March after being punished with objects by their parents.

"Section 43 sends parents and teachers the message that it's okay to hit children, that it's `justified,' which in law means `morally correct' and `rightful,'" said Corinne Robertshaw, founder and national co-ordinator of the Repeal 43 Committee. "We say there is a connection between giving that message and the fact that a lot of children are injured during the course of corporal punishment."

Sometimes, studies have found, parents don't realize how hard they are hitting. And sometimes a child can build tolerance to pain so that the parent must hit harder to get results. Physical punishment, in such cases, can result in abuse.

"Most cases of child physical abuse occur during episodes of physical punishment," says a Joint Statement on Physical Punishment of Children and Youth, signed by more than 70 Canadian health and child care organizations, including Toronto Public Health.

"Physicians should actively counsel parents about discipline," the Canadian Pediatric Society said in a new policy directive yesterday, "and should strongly discourage the use of spanking."