The Supreme Court of Canada has declared that a law that allows police to wiretap phones without a warrant during emergencies is unconstitutional and has given Parliament one year to reword the law.

But police can continue to perform emergency wiretaps for 12 months while Parliament makes adjustments to the law.

The court expressed concerns that the section of the Criminal Code that allows police to tap phone conversations in an emergency did not include a provision that would require police to later notify those persons whose private phone calls had been tapped.

In most cases when police intercept phone conversations, they need to obtain a warrant from the court. They must then notify the people whose conversations were intercepted within 90 days after the warrant expires.

But in Section 184.4 -- which allows for emergency wiretapping in situations in which lives and property might be at risk -- there is no provision requiring that notice ever be given.

That is unfair, the court ruled unanimously.

"In its present form however, s. 184.4 contains no accountability measures to permit oversight of the police use of the power," the justices wrote.

"It does not require that ‘after the fact' notice be given to persons whose private communications have been intercepted. Unless a criminal prosecution results, the targets of the wiretapping may never learn of the interceptions and will be unable to challenge police use of this power."

The court ruled that while Section 184.4 was unconstitutional, they had decided to suspend that declaration for 12 months to allow Parliament to rewrite and correct the law.

The ruling stems from a kidnapping in British Columbia in 2006 in which a man named Peter Li, his wife Jennifer Pan, and their friend Xiao Chang, were kidnapped.

The six people who beat and kidnapped them demanded $10 million. They eventually got $1.3 million in ransom after holding their victims for 25 days.

Police immediately began to intercept phone calls from the kidnappers to Li's daughter, Mary. Within 24 hours, police got the proper warrants they needed.

But when the case went to trial, the trial judge found the law allowing emergency wiretaps breached Section 8 of the Charter, which protects people from unreasonable search and seizure. That judge later allowed the intercept evidence to be admitted into evidence, saying it would not bring the administration of justice into disrepute.

The accused were eventually sentenced to prison terms ranging from 10 to 18 years.

In its ruling, the Supreme Court recognized the police's need for emergency wiretaps.

"In our view, there is little doubt that the objective of preventing serious harm to persons or property in exigent circumstances is pressing and substantial," the justices wrote.

But they added there was also a need to inform intercepted parties that their privacy had been invaded as part of a police investigation.

"The obligation to give notice to intercepted parties would not impact in any way the ability of the police to act in emergencies. It would, however, enhance the ability of targeted individuals to identify and challenge invasions to their privacy and seek meaningful remedies," the justices wrote.

The court's most recent additions, Justice Michael Moldaver and Madam Justice Andromache Karakatsanis, combined to write the judgment.