This view might be controversial but here goes. If someone is suspected of a major crime (rape, serious assault, murder, major theft), maybe it's okay for law enforcement to gain access to that person's online accounts.
People might say "but if the government has the power to do that, one day they could do it to you, or they could use those powers to oppress anybody who criticises the government". But isn't that like saying "if you build prisons then one day an authoritarian government might put any critic of the government in those prisons"?