It's a case that could have wider privacy implications, including for smartphones and tablets.
There has been no single guideline for searching cellphones during arrests, though the court last year found that special authorization is needed to search computers and cellphones during the execution of a search warrant. That case involved searches of a location, such as a house, and didn't specifically address a search during an arrest.
The decision is also likely to deal with password protection, an issue mentioned in the ruling by the lower court.
Thursday's case comes out of a 2009 armed robbery in Toronto where police found a cellphone when they patted down Kevin Fearon and Junior Chapman, the men they were arresting.
When police looked at the text messages on the phone, they found a draft message that referred to jewelry and included the phrase "we did it."
They also found a photo of a handgun.
The police can search a cellphone if it's reasonable to believe there may be evidence of a crime on it, or if they think it holds information needed to prevent another crime.
In this case, officers thought it was urgent to find the handgun used in the robbery and to find the jewelry before it could be hidden or sold.
The police applied for a search warrant months later, which was granted.
The trial judge found the text message and photo could be submitted as evidence and Fearon was found guilty.
In his appeal, Fearon's lawyer argued that his client's right to be free of unreasonable search and seizure was breached.
The Ontario Court of Appeal dismissed the appeal in a unanimous decision.
"If the cellphone had been password protected or otherwise 'locked' to users other than the appellant, it would not have been appropriate to take steps to open the cellphone and examine its contents without first obtaining a search warrant," Robert P. Armstrong wrote in the February 2013 decision.
The B.C. Civil Liberties Association intervened in the lower court hearing and in the Supreme Court case to argue that police should only search a cellphone in an emergency.