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As ABC News reports, the law which allows agencies to do such things is the Stored Communications Act (SCA), part of the 1986 Electronic Communications Privacy Act.

The SCA allows investigating bodies to access email accounts provided by standard services including Google and Yahoo. Once granted a warrant, any “government entity” can force a provider to disclose “contents of a wire or electronic communication” that has been in storage for up to 180 days, providing there is reasonable cause to believe a crime is being committed.

If electronic communication has been stored for over 180 days, a government agency must be granted a subpoena or court order.

“The government can’t just wander through your emails just because they’d like to know what you’re thinking or doing,” Stewart Baker, former assistant secretary at the Department of Homeland Security told the AP. “But if the government is investigating a crime, it has a lot of authority to review people’s emails.”

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