The 9th Circuit Court of Appeals, which is located in San Francisco, has ruled that law enforcement needs a probable cause warrant to read copies of your electronic messages that have been stored less than 180 days even if you have already downloaded or read them. The ruling also prohibits employers from getting the contents of employee emails or text messages from the service provider without employee consent. See, Quon v. Arch Wireless Quon was an Ontario, California Police Officer who was provided with a two way alphanumeric pager by the Ontario Police Department. He used it to send both work and personal messages. Quon sued Arch for violation of the Stored Communications Act and the Ontario Police Department for violation of the Fourth Amendment. The 9th Circuit ruled that Arch did violate the Act and that the Police Department violated the Fourth Amendment.
The Electronic Frontier Foundation provides an analysis of the opinion on the Deeplinks Blog. Although many headlines would have you believe that this is a broad ranging opinion that prohibits employers from reading text messages in general, the opinion may be more limited than that. Quon was a civil service employee working for a government agency that was also a law enforcement agency. The Ontario Police Department is subject to the Fourth Amendment, but most employers are not. The Fourth Amendment limits government not individuals. However, there may be other limits on the ability of individuals to snoop. The 9th Circuit is also famously liberal so it remains to be seen how other courts will interpret the Stored Communications Act as it applies to employers seeking information transmitted via devices owned and paid for by the employer.
Ironically, the 9th Circuit is the appellate court on which Judge Kozinski, who got into some trouble due to a personal web page, sits.