An elderly man has been ordered to stand trial for allegedly raping his wife almost half a century ago, even though it was not considered a crime at that time.

If the man had been tried at the time, in 1963, he would have been found not guilty because of the principle of matrimonial consent.

The centuries-old common law principle was applied until the 1970s and held that the act of marriage implied consent.

But in a majority decision, two judges of the South Australian Court of Criminal Appeal have ruled the man, who is 79, can no longer claim matrimonial consent as a defence.

Chief Justice John Doyle said the decision was based on a 1991 High Court ruling which rejected the principle.

"In 1963 one would have found statements by judges and writers of textbooks to the effect that at common law, a husband could not be guilty of raping his wife," he wrote.

"Since then it has become clear that it is no longer the law."

Dissenting view

The judgment also noted South Australia was the first state to make rape in marriage a crime through legislation introduced in 1976.

But dissenting judge, Justice Tom Gray, said the man should be dealt with based on the laws of the time.

"This is part of a wider principle that people should be judged by their contemporaries and by contemporary standards and beliefs, rather than many years later by people with perhaps very different standards and beliefs," he wrote.

"His conduct in 1963 was at that time lawful.

"Had he been tried in the years immediately following the alleged conduct, he would have been acquitted."

Law Society of South Australia president Ralph Bonig said the ruling was bound to divide the legal community.

"You've got a balancing of 21st century values - because no one would condone rape in marriage - against 1963 law, so to that extent it is contentious", he said.

"I don't think it's going to open, to use a term, the floodgates because you're going to have to have a lot of similar fact cases before it impacts on other events."

The accused man can still seek to appeal against the decision in the High Court.

He can also try to have the charges thrown out in the District Court by arguing that too much time has passed for him to receive a fair trial.