Reported in the Wall Street Journal: A federal appeals court in Ohio has revived a lawsuit against a company accused of helping a husband spy on his wife and her online friend in violation of state and federal wiretap laws.

The case is one of several in recent years to highlight the increasing presence of easy-to-use electronic spy tools in domestic life and divorce proceedings, where evidence of infidelity can carry a tremendous advantage.

The Sixth U.S. Circuit Court of Appeals ruled 2-1 that a man in Tampa, Fla., could sue the maker of a computer program called WebWatcher that was allegedly used to intercept his emails and online chats with an unhappily married woman in Ohio.

Javier Luis’s 2012 lawsuit against Awareness Technologies said he struck up a relationship with Catherine Zang in 2009, after meeting her in an America Online chat room for discussions of metaphysics.

Ms. Zang’s husband at the time, Joseph Zang, installed WebWatcher on the family computer to monitor his wife, according to Tuesday’s ruling. The program recorded emails and instant message between Mr. Luis and Ms. Zang and routed them to Awareness Technologies’s servers in California for Mr. Zang to review later through his WebWatcher account.

Mr. Zang monitored his wife’s online relationship with Mr. Luis — the two never met in person — for several months and then used the cache of communications “as a battering ram against Cathy” in their divorce proceedings the next year, forcing her to accept his terms, the lawsuit said.

Mr. Luis’s lawsuit alleged that Awareness markets WebWatcher to suspicious spouses, “enticing them with the lure of finding out everything that goes on in the targeted computer’s private accounts.”

The federal Wiretap Act prohibits intentionally intercepting or attempting to intercept any wire, oral, or electronic communication. …

Lawyer Mark Pickrell, the interim head of Vanderbilt Law School’s appellate litigation clinic, which represents Mr. Luis, said the ruling could make waves beyond the market for personal snooping tools.

While employees give consent to be monitored as part of their jobs, for instance, people they communicate with do not. Firms that provide employee monitoring services could be more exposed, he said.

“It will affect a lot of monitoring that takes place,” Mr. Pickrell said.