For most things privacy related in Canadian law, it comes down to what a judge feels Canadians think is reasonable. A couple of days ago the Ontario court of appeal ruled that police do not need a warrant to search your cellphone if it’s not password protected.
“In this case, it is significant that the cell phone was apparently not password protected or otherwise “locked” to users other than the appellant when it was seized. Furthermore, the police had a reasonable belief that it would contain relevant evidence. The police, in my view, were within the limits of Caslake to examine the contents of the cell phone in a cursory fashion to ascertain if it contained evidence relevant to the alleged crime. If a cursory examination did not reveal any such evidence, then at that point the search incident to arrest should have ceased”. –  of R. vs Fearen
What hasn’t been documented in anything I’ve seen is also the fact that in this case the police argued they were looking at the cell phone not for evidence of the crime, but to determine ownership (proof it wasn’t stolen).
If the telephone number had been written or inscribed on the exterior of the cell phone or visible or easily found when the phone was opened, any further search obviously could not be justified as a cursory inspection to determine ownership. Likewise, in a case where there was no reason to doubt the arrested party’s ownership of the phone and no link between ownership and the offence for which the person was arrested, a search of the stored data in the phone could not be justified on the basis that the police were simply trying to determine who owned the phone. –  of R. vs Fearen
In summary, if you’re Canadian and don’t want law enforcement to have the authority to search the contents of your cellphone without a warrant, you should setup a password protected screen lock on the device. You may also want to consider an identifier on the locked screensaver that defines your identity to further the above claim, but also provide reference in case your lost or stolen cellphone is ever found.