"MPs should be aware that the legal position in terms of the security of their emails is either unsure or that American security services can get copies of them if they want them."
Should Microsoft be let off then there will likely be implications for the security of all other extraterritorially stored data.
MPs and peers saw their mailboxes migrated to Microsoft's Office 365 cloud servers in July 2014.
Under parliamentary law, British security services are not allowed to access the emails of MPs.
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