So what does this have to do with privacy? Well, the stored communications act was written back in the days when email was much more akin to a mailbox. Because of this, it treats old email in a manner which is similar to how one might treat abandoned mail, and provides a mechanism in 18 U.S.C. 2703(d) to allow the government to get access to it without a warrant.
Actually, it provided a mechanism to allow the government to get access without a warrant. That changed with the case of U.S. v. Warshak, which found the government's use of section 2703(d) to obtain incriminating emails without a warrant violated the fourth amendment.
The facts of the case are extreme, and make for entertaining reading. The main defendant, Steven Warshak, owned Berkeley Premium Neutraceuticals, the company behind the once ubiquitous commercials for Enzyte. According to the opinion, Warshak had owned a number of other businesses. However, Berkeley stood out, both because of the success of Enzyte, and because of its extremely slimy business practices. A sample:
in November 2003, Berkeley hired a company called West to handle “sales calls that were from . . . Avlimil or Enzyte advertisements.” During the calls, West’s representatives asked customers if they wanted to be enrolled in the auto-ship program, and over 80% of customers declined. When Warshak learned what was happening, he issued instructions to “take those customers, even if they decline[d], even if they said no to the Auto-Ship program, go ahead and put them on the Auto-Ship program.” A subsequent email between Berkeley employees indicated that “all [West] customers, whether they know it or not, are going on [auto-ship].” As a result, numerous telephone orders resulted in unauthorized continuity shipments.
Those practices eventually led to a 112 count indictment, and the government obtaining thousands of incriminating emails from Warshak's service provider without a warrant under section 2703(d) of the stored communications act. After his conviction, Warshak appealed to the Sixth Circuit court of appeals arguing (among other things) that the emails were obtained in violation of the 4th amendment, and therefore should have been excluded as evidence.
While the Sixth Circuit upheld Warshak's conviction, it agreed that the warrantless search of Warshak's emails violated the fourth amendment. First, it established that Warshak had a subjective expectations that his emails would remain private. Indeed, the court said the very fact that the emails contained so much incriminating information was evidence that Warshak saw them as private correspondence. Next, the court asked whether the expectation of privacy in emails was one society was prepared to recognize as reasonable. To answer, the court addressed the heavy reliance of modern society on email, and analogized it to other types of communication that were traditionally protected under the fourth amendment. In the end, it concluded that
because they did not obtain a warrant, the government agents violated the Fourth Amendment when they obtained the contents of Warshak’s emails. Moreover, to the extent that the SCA purports to permit the government to obtain such emails warrantlessly, the SCA is unconstitutional.
The decision didn't do much for Warshak. The court also held that the government had been relying in good faith on the act, and so the emails shouldn't be excluded. However, it will help everyone else down the line, because the good faith rule can't be used to justify actions that are clearly inconsistent with the court's holding.