Back in 2014, the US Government issued a search warrant to Microsoft asking the company to hand over details about customers that are held on servers outside of the US, specifically a customer with emails stored in Ireland. Today, a new report published in the National Law Journal is showing that to perhaps further challenge the government's argument in the battle, Microsoft is citing a recent opinion of the Supreme Court that finds that U.S. laws can not apply to global conduct without Congressional approval.
In their report, The National Law Journal cites a letter to the US Court of Appeals written by a Microsoft lawyer. In the letter, Microsoft notes that the government is using a statute to seize emails stored on a foreign computer. As The National Law Journal notes, Microsoft finds that the "presumption against extraterritorial application applies," and, "Congress, as required, has not made its intent clear that the statute applies abroad."
This "presumption against extraterritorial application," dealt with in the recent Supreme Court ruling, basically says that unless a law specifically includes a cross-nation application, it must be presumed to be US only.
The Supreme court ruling that Microsoft also cites in its letter involved a ruling in the case of RJR Nabisco v. European Community. A decision in that case was similar to Microsoft's battle with the US Government, where the justices found that racketeering law applies extraterritorially in some circumstances, but a private plaintiff must show an injury within the United States to recover damages.
Microsoft lost a court case in the Ireland email case late in 2014, but has appealed.