In 2013, Microsoft have actually asked US SDNY (and by extension the federal government) whether there is a legal basis for a warrant issued since that the data

In 2013, Microsoft have actually asked US SDNY (and by extension the federal government) whether there is a legal basis for a warrant issued since that the data is in Ireland (and was never brought to the US), and Microsoft thinks that since the subsidiary controls the data instead of themselves US SDNY (and FBI) would need to activate Irish MLAT services. It actually went to the Supreme Court (https://supreme.justia.com/cases/federal/us/584/17-2/ https://supreme.justia.com/cases/federal/us/584/17-2/), and the result? Well, the Congress have passed the Clarifying Lawful Overseas Use of Data Act (https://www.govinfo.gov/content/pkg/PLAW-115publ141/pdf/PLAW-115publ141.pdf#page=867 https://www.govinfo.gov/content/pkg/PLAW-115publ141/pdf/PLAW...) that basically states that the US has extraterritorial jurisdiction on all data held by US companies, making the case moot.