If you happen to send an email to one of the 400 million people who use Google's Gmail service, you shouldn't have any expectation of privacy, according to a court briefing obtained by the Consumer Watchdog website.

In a motion filed last month by Google to have a class action complaint dismissed, Google's lawyers reference a 1979 ruling, holding that people who turn over information to third parties shouldn't expect that information to remain private.

From the filing (emphasis added):

Just as a sender of a letter to a business colleague cannot be surprised that the recipient’s assistant opens the letter, people who use web-based email today cannot be surprised if their communications are processed by the recipient’s ECS provider in the course of delivery. Indeed, “a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties.” Smith v. Maryland, 442 U.S. 735, 743-44 (1979). In particular, the Court noted that persons communicating through a service provided by an intermediary (in the Smith case, a telephone call routed through a telephone company) must necessarily expect that the communication will be subject to the intermediary’s systems. For example, the Court explained that in using the telephone, a person “voluntarily convey[s] numerical information to the telephone company and ‘expose[s]’ that information to its equipment in the ordinary course of business.” Id. at 744 (emphasis added).

It should be noted that in January 2012, Supreme Court Justice Sonia Sotomayor cited the same case as Google (Smith v. Maryland), but she argued that business transactions over the phone or internet are not automatically disentitled to Fourth Amendment protection.

“Google has finally admitted they don’t respect privacy,” said John M. Simpson, Consumer Watchdog’s Privacy Project director, in a news release. “People should take them at their word; if you care about your email correspondents’ privacy don’t use Gmail.”

The lengthy brief goes on to maintain that Google uses automated processes to sift through email for the purposes of providing spam filters, relevant advertising, and other features of the Gmail service. The opposition complaint however, takes issue with this, saying the company is instead trying "to capture the [email] authors' actual thoughts for Google's secret use."

Google argues the terms of service and privacy policy of Gmail lays out their automated processes of scanning email — and by agreeing to use the service, users are bound to those terms.

Outside users — such as someone sending an email from Yahoo mail to a Gmail user — "must necessarily expect that their emails will be subject to automated processing" according to the briefing. This automated processing, Google argues, is essential to making the Gmail service work.

The company's reasoning shouldn't come as a huge shock. Google Executive Chairman Eric Schmidt told a CNBC interviewer in 2009 the company is bound to the federal terms of the U.S. PATRIOT Act.

"If you have something that you don't want anyone to know, maybe you shouldn't be doing it in the first place," Schmidt said. "But if you really need that kind of privacy, the reality is that search engines, including Google, do retain this information for some time. And ... we're all subject, in the United States, to the Patriot Act, and it is possible that that information could be made available to the authorities."

A Google spokesperson told Business Insider the following via email:

"We take our users’ privacy and security very seriously; recent reports claiming otherwise are simply untrue. We have built industry-leading security and privacy features into Gmail -- and no matter who sends an email to a Gmail user, those protections apply."

Here's the full brief:

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