Screenshot by Steven Musil/CNET

Apple's next legal battle is not over patents, but missing text messages instead.

The tech titan must answer to a federal lawsuit filed in May that alleged the company didn't notify consumers about potential headaches when ditching their iPhones, US District Judge Lucy Koh of San Jose, Calif., said Tuesday.

The company's iMessage service, which allows users to send missives to one another through Apple's encrypted communication network, doesn't work on phones powered by Google's Android, Microsoft's Windows Phone or any other non-Apple operating system. Yet, when some consumers switched away from iPhones, their iMessages were not rerouted to their new phones. Worse, affected users usually think their message are delivered even though they never are while never being informed of friends' messages that are sent but never received.

That misstep, the suit claims, led to disruptions in a customer's wireless service contract, violating a California unfair competition law in the process. The order comes just a few days after Apple released an iMessage fix online.

Apple declined to comment for this story.

The suit underscores exactly how important text communications have become. But it also shows the dangers both of Apple's approach to mobile software and the ever-escalating messaging war taking place in the tech industry. Google pushes its Hangouts program onto Android and Gmail users while Facebook has gone to great lengths to capture more of mobile messaging, using its Messenger service and acquisition of WhatsApp to further that goal.

Apple's messaging approach has matched its philosophy of keeping users of its hardware and software within its tightly controlled ecosystem. But with iMessage, the suit alleges, Apple went too far.

Plaintiff Adrienne Moore said Apple failed to communicate this problem and obstructed the use of her new Samsung Galaxy S5. She'd activated the new phone under her existing Verizon Wireless contract after switching from an old iPhone 4 in April of this year.

Moore is seeking unspecified damages and class-action status for the lawsuit. That means any monetary amount awarded could trickle down to all users affected by the iMessage issue. Judge Koh says Moore has a right to attempt to prove Apple did in fact obstruct her use of an Android phone and hampered full use of her Verizon contract.

"Plaintiff does not have to allege an absolute right to receive every text message in order to allege that Apple's intentional acts have caused an 'actual breach or disruption of the contractual relationship,'" Koh wrote.