Yahoo is asking a federal judge to dismiss a potential class-action lawsuit accusing the company of violating privacy laws by scanning email messages in order to surround them with ads.The company argues in court papers filed last week that its scans don't violate the Electronic Communications Privacy Act, on the theory that Yahoo users explicitly consent to the company's practices by accepting the terms of service.Yahoo says it unambiguously informs users about its policies in the terms of service, which state that the company's systems “scan and analyze all incoming and outgoing communications content sent and received from your account ... to match and serve targeted advertising and for spam and malware detection and abuse protection.”This lawsuit was brought in October on behalf of non-Yahoo email users who send email to Yahoo account holders. The non-Yahoo users allege that they never consented to scans of their messages.But Yahoo argues that it doesn't need permission from non-Yahoo users, because federal privacy law only requires consent from one party to a conversation, which in this case would be the Yahoo account holders.“The clear terms of Yahoo’s agreement with its users demonstrate that all users consent to the scanning and analyzing of their email. If such language is deemed inadequate to obtain consent, it is hard to imagine what text would suffice,” the company says.Yahoo also says that it doesn't violate a California privacy law that prohibits companies from intercepting communications without all parties' permission. Yahoo argues that applying the California law to activity like automated email scans “would potentially turn ordinary and widespread computer use into criminal activity.”The lawsuit against Yahoo is similar to one litigation accusing Google of violating the federal wiretap law by serving contextual ads in Gmail. In that case, U.S. District Court Judge Lucy Koh in the Northern District of California rejected Google's motion to dismiss the lawsuit.Koh -- who also is presiding over the Yahoo lawsuit -- said in the Google case that non-Gmail users don't consent to have their messages scanned. Koh also ruled that Gmail users don't consent to the interceptions because Google's terms of service don't clearly explain its scanning program. Google has scanned Gmail messages since launching the service in 2004. Yahoo only started doing so in 2011.