EFF supported Microsoft's challenge to a search warrant ordering it to disclose the contents of email stored in Dublin, Ireland.

In December 2013, the federal government applied for a search warrant to obtain the contents of emails and other details from a user account hosted by Microsoft. While the non-content records were stored in the United States, Microsoft discovered that the contents of the emails were stored on a server located in Dublin, Ireland. It refused to turn the emails over to the government, arguing that a U.S. judge had no authority to issue a search warrant for records stored abroad. A federal magistrate judge disagreed with Microsoft in April 2014, ordering it to turn over the emails.

Microsoft appealed that decision to the U.S. district court and we filed an amicus brief in support of them. Our brief explained that Microsoft's act of copying email to turn over to the government is a Fourth Amendment "seizure" that takes place abroad, meaning the government could not rely on a search warrant to get them but instead had to go through the U.S.-Ireland Mutual Legal Assistance Treaty (MLAT) process. The district court rejected Microsoft's appeal in July and Microsoft appealed the decision to the Second Circuit Court of Appeals.

In the Second Circuit, we signed onto a joint amicus brief with the Brennan Center for Justice, the American Civil Liberties Union and the Constitution Project urging the appeals court to overturn the lower court's decision. The Second Circuit held that police cannot use U.S. warrants to compel U.S. Internet companies to disclose users’ email and digital content stored outside the United States.

In 2017, The U.S. Supreme Court agreed to review the case, and EFF filed a brief in support of Microsoft. However, with the passage of the CLOUD Act in early 2018, the Supreme Court dismissed the case as moot and vacated the lower court rulings.