The 11-page ruling in British Columbia said a parole denial in December for Robert Latimer, 55, "cannot be reasonably supported in law," the Vancouver Sun reported.
Latimer is serving a life sentence for the mercy killing of his severely disabled 12-year-old daughter Tracy on Oct. 24, 1993, by carbon monoxide poisoning in a truck on his farm in Wilkie, Saskatchewan, northwest of Saskatoon.
The incident sparked a firestorm of controversy in Canada over euthanasia and the rights of the disabled.
Latimer said in December he wouldn't be able to return to farming after all the time in jail, and requested day parole in Ottawa, so he could become a lobbyist for euthanasia, the report said.
Latimer has been classified as a minimum-security offender since 2003 and won't be released until a bed is found for him at an Ottawa halfway house, the report said.