This Ruling Just Made It Harder to Spy on Your Spouse by Jeff John Roberts @FortuneMagazine August 18, 2016, 11:36 AM EDT E-mail Tweet Facebook Linkedin Share icons Joseph Zhang became suspicious of his wife Catherine’s online activities, so he installed software called WebWatcher on their home computer in Ohio to track her. The fallout was not just a divorce, but a landmark court ruling that could have long-term implications for both users and makers of so-called spyware. According to an appeals court in Cincinnati, the maker of the spyware used by Zhang violated federal and state wire-tapping laws by intercepting the messages of a Florida man, Javier Luis, who had been communicating with Catherine in an America Online chatroom called “Metaphysics.” The legal case begin in 2010 not long after Zhang used messages captured with the spyware to obtain leverage in divorce proceedings, even though a court said the relationship between his wife and Luis was “apparently platonic.” In response, Luis sued not only Zhang, who settled the case, but also Awareness Technologies, arguing the software maker should have known that customers of its WebWatcher product would use it to illegally intercept messages. A lower court sided with Awareness, and threw out the case on the grounds only Zhang, not Awareness, had intercepted the messages. But in a 2-1 decision, the Cincinnati appeals court overturned that filing. The higher court found Awareness’s activities were not just limited to selling the product, but that the company played an active role in the process by capturing messages “in flight” and rerouting them to its servers in California. The decision also pointed to marketing materials from Awareness that touted how WebWatcher “records all PC activity including emails, IMs, websites visited, web searches, Facebook/MySpace activity, and anything typed in real time” and how the software had an “Alert Word” feature that takes screenshots whenever a user types certain words. According to Luis, he felt surprise and dismay upon learning Awareness had intercepted his messages, and claimed the company violated the law by sharing “private and potentially embarrassing facts” with other people like Zhang. All of this led the court to look favorably on his claim that Awareness had performed an illegal wire-tap. Get Data Sheet, Fortune’s technology newsletter. The company did not reply to a request for comment about the decision by the appeals court, which sent the case back to the lower court for a closer look. In the bigger picture, the case is a worrisome development for spyware makers, many of which market their products to consumers who want to keep tabs on partners or loved ones. The companies that provide such services, especially ones based on cloud-based software, will face an enormous business challenge if courts consider them to be participants in illegal wire-taps. The dissenting judge in the case sided with Awareness, arguing it did not actively engage in the wire-tapping, and that the court’s ruling would lead to a “muddle” of uncertainty over when companies should be liable for their software. You can read a copy of the ruling here (I’ve underlined some of the key bits).