A judge from the United States ordered Yahoo Inc to face a class-action lawsuit for illegally intruding at the content of emails sent from non-Yahoo Mail accounts and sent to Yahoo Mail subscribers and utilizing the data to boost advertising profit.

U.S. District Judge Lucy Koh in San Jose, California said people who sent emails to or received emails from Yahoo Mail subscribers since Oct 2, 2011 may collectively file a case as a group under the federal law, Stored Communications Act for alleged violations of privacy.

She also explained a class suit of non-Yahoo Mail subscribers in California from Oct 2, 2012 may file a case against the company under the Invasion of Privacy Act in the state.

Yahoo allegedly collects this data from all of its 275 million subscribers. Presumably, Yahoo gathers the information in a similar automatic process it utilizes to scan for malware and spam. Purportedly, Yahoo snooped through the emails' attachments, as well as the subscribers' searched keywords that would boost their advertisings. In doing so, Yahoo gathered 79 percent of its revenue in 2014 from display and search advertising.

The Stored Communications Acts' Fourth Amendment-like provisions protect online communications, put limit to commercial entities' ability to share the messages and its content sent through the web, unless the sender explicitly agrees to it.

The Invasion of Privacy Act in California was implemented to avoid wiretapping any form of conversation where there is a logical anticipation that is not being recorded or overheard. At the same time,  it will be for the court to interpret what "reasonable expectation," mean in Yahoo's case, the supposed lack of consent is possibly a critical factor in the judgment.

Yahoo's defense against the class action suit tried to invoke the same grounds on a similar case in March 2014, where Koh ruled in favor of Google. Koh explained why she permitted the case against Yahoo to pursue, and not the case against Gmail of Google, because in the latter it wasn't clear which regular users of Gmail agreed to Google's rules and which did not.