They didn't - as I said before, this kind of communication is commonplace between large tech properties and governments, other large companies, NGOs, etc. It wasn't anything like a direct order. Local law enforcement, city councils, lobbyists, PR people, anyone with information or access will often have a more direct line to Twitter, Youtube, etc than the 'report' button.
There do exist direct orders to reveal or conceal information that do require a judge to sign, things like National Security Letters. It's remarkable that NSLs and other compelling documents don't get more play in these conversations. They actually are what people think these friendly emails are.
