The decision will have a bearing on the billions of private texts sent each year by Canadian wireless customers.
Wireless giant Telus (TSX:T) argues police need wiretap authorization to seize private text messages from a customer's mobile device.
But the federal government says that would clog the courts with thousands of wiretap applications each year.
The case arises from a warrant the Ontario Superior Court granted to police in Owen Sound, Ont., that ordered Telus to turn over texts from two of its customers.
The warrant forced the company to email police a copy of the customers' texts every day for two weeks, unbeknownst to the owners of the phones.
Telus appealed to the Supreme Court after losing its initial bid to quash the warrant.
The company's lawyers argued police need wiretap authorization under the Criminal Code to seize private text messages.
"The intrusion on a person's privacy is identical whether the police surreptitiously listen in to your conversations while they are occurring or surreptitiously read copies of your private communications that are obtained directly from the means required for delivery of the communication," they say in written arguments.
In addition, Telus wants the Supreme Court to clarify if its decision applies only to already-sent messages, or if the ruling also allows police to pre-emptively seek permission to seize texts sent at a later date.
What Telus is asking from the court is "illogical, unworkable, and inconsistent" with the Criminal Code, say government lawyers.
"To accept Telus' argument would mean that any time the police seek to acquire the contents of a private communication from any service provider's computer and by any means, it constitutes an interception," say their written arguments.
"Telus' argument leads to absurd results."
The case before the Supreme Court is one of several involving privacy concerns in an age of electronic communication.
Earlier this year, Ontario's highest court ruled it was OK for police officers to look through someone's cell phone if it is not password protected. However, the Court of Appeal for Ontario said a search warrant is needed if the phone has a password or is otherwise locked to anyone other than its owner.
The password case came after a man was arrested after a jewelry stall at a Toronto flea market was robbed, and police found pictures of a gun and cash as well as a text message about jewelry on his phone.Suggest a correction