Montreal (AFP) - Canada's Supreme Court acted to protect children in the fast-growing world of cyberspace, enabling judges to prohibit those convicted of sexual offenses against minors from using the internet.

"The record demonstrates that the internet is increasingly being used to sexually offend against young people and that sex offenders who target children are more likely to re-offend," Justice Andromache Karakatsanis wrote for the majority in a hundred-page ruling.

The case concerned incest and child pornography. The accused man, sentenced to nine years in prison in 2013 by a court in British Columbia, had abused his daughter between 2008 and 2011.

In addition to upholding his prison sentence, the court prohibited him from accessing the internet, retroactively applying a provision to the criminal code added after the offenses took place.

The country's previous Conservative government introduced a provision in its Safe Streets and Communities Act of 2012 prohibiting internet use for sex offenders.

In its seven-to-two ruling, the court banned internet access to anyone convicted of sexual offenses against minors before 2012 -- rejecting the constitutional principle guiding courts to impose lesser punishments if the criminal code is changed between the time offenses are committed and sentencing is carried out.

"The rate of technological change over the past decade has fundamentally altered the social context in which sexual crimes can occur," the ruling said, adding that "monitoring an offender's use of the internet can limit an offender's opportunities to offend and prevent this harmful behavior."