WARNING: Content of this story may offend some readers. The story deals with bestiality.​

The Supreme Court of Canada has upheld the acquittal of a British Columbia man in a decision that defines the crime of bestiality as penetration involving a person and animal.

The B.C. man was found guilty three years ago of 13 counts arising from years of sexual molestation of his two step-daughters.

The charges included one count of bestiality under the Criminal Code, stemming from sexual activity involving the older girl and the family dog.

The man successfully challenged the bestiality conviction in the B.C. Court of Appeal based on the fact the activity did not involve penetration. (The man cannot be named to protect the identities of the step-daughters.)

In a 6-1 decision Thursday, the Supreme Court affirmed that ruling, rejecting the notion bestiality is an offence encompassing sexual activity of any kind between a person and an animal.

At issue was whether updates to the Criminal Code in 1955 and 1988 altered the meaning of the crime.

"The term 'bestiality' has a well-established legal meaning and refers to sexual intercourse between a human and an animal. Penetration has always been understood to be an essential element of bestiality," wrote Justice Thomas Cromwell on behalf of the court.

"Parliament may wish to consider whether the present provisions adequately protect children and animals. But it is for Parliament, not the courts, to expand the scope of criminal liability for this ancient offence."

In a dissenting opinion, Justice Rosalie Abella said she had a great deal of difficulty accepting that in modernizing amendments to the Criminal Code, "Parliament forgot to bring the offence out of the Middle Ages."

A good case can be made that by 1988, Parliament intended, or at the very least assumed, that penetration was irrelevant, she wrote.