The EU has intervened in an ongoing case between Microsoft and the US government to ensure the US Department of Justice (DoJ) understands European data laws.
The case, ongoing since 2013, has seen the DoJ demand that Microsoft hands over data related to a US criminal case, even though the data is stored in a server located in Dublin. The EU claimed that because the data would have to be moved from Europe to the US, it would come under EU data protection laws.
Now, the European Commission has submitted an amicus brief - information filed by non-litigants to give the court a better understanding of a matter - to help it make a decision about whether the data should be handed over or not.
"This case raises the question whether, under the US Stored Communications Act, US courts can require a US-based service provider to produce the contents of a customer's email account stored on a server located outside the United States, in this case Ireland," the EU's notice reads.
"Given that the transfer of personal data by Microsoft from the EU to the US would fall under the EU data protection rules, the Commission considered it to be in the interest of the EU to make sure that EU data protection rules on international transfers are correctly understood and taken into account by the US Supreme Court."
The DoJ has, however, responded, saying it would pursue its claim and insist Microsoft could comply with its warrant for the data by undertaking acts entirely in the United States.
It also states that Microsoft never divulged that it would need to comply with Irish or EU data laws for "disclosing in the United States any communications stored at its Dublin datacenter."
The DoJ added: "if an actual conflict of laws were to arise, our judicial system is equipped to handle that scenario. The government could exercise discretion to pursue alternate channels, where available."
The long-running case initially saw the DoJ's warrant for the data upheld in court, but last year Microsoft won on appeal, and again in the Second Circuit, both ruling that US authorities can't demand access to emails of foreign users held in data centres outside the country using standard search warrants.
