The CRTC introduced the new code in June, 2013 to give consumers better protection against high cellphone roaming charges and wireless contract cancellation fees.
Wireless operators including Rogers Communications, Telus and BCE Inc. launched legal action last July after raising concerns that some provisions of the code would apply retroactively to all of their customers once fully implemented.
In writing the decision for the three-member panel, Justice Denis Pelletier said the CRTC "has the right to make the wireless code applicable to contracts concluded before the code came into effect."
Once in force, the wireless code would require carriers to limit early cancellation fees, data roaming fees and overage charges, and imposes restrictions on the locking of wireless devices.
The code will apply to all customers, regardless of when they signed contracts.
"Given the CRTC's intention to put more information into the hands of consumers so as to increase the dynamism of the market, it is reasonable to have all consumers on the same footing as soon as possible," Pelletier wrote.
OpenMedia, which represented Canadians throughout the court challenge with legal experts, hailed the decision as a victory.
"This is a major win!" OpenMedia campaigns manager Josh Tabish said in a release. "By standing together, Canadians fought back against telecom giants in court and won."
Also on HuffPost