Re: The usual
From a legal perspective, the DoJ has the law and leverage at its side
Not in Europe, it doesn't. Quite the reverse; the EU is legally required to refuse its demands.
As far as I can see, the whole problem is that from the DoJ's perspective, EU law is simply not in play. The US DoJ has asked a US company to provide data held by one of its subsidiaries. As Microsoft HQ as owner has the means to acquire such data, the DoJ considers this a viable request that Microsoft has to fulfil or face fines.
I agree with you that if this request in an EU legal context would be need a lot of extra motivation before it would yield an appropriate warrant (it's not impossible, but EU barriers are *much* higher), but the whole point of this conflict is the inside track approach that the DoJ relies on to avoid all these pesky EU privacy laws.
That's why it's so dangerous to have your HQ in the US - as owner you're deemed to have this access and it's not the DoJ's problem if that causes you to breach the law in the place where you hold that data. You're the company owner, you have to comply. End of story. Life must be grand if you can just ignore the existence of anyone else on this planet.
The legal representatives of a *very* large US company I met in Brussels told me that they found that even having just a man and a dog in a shed in the US can still create problems, but if your HQ is in the US you're apparently simply not in a position to fight this off.
That's why this is a game of very high stakes poker, and why the EU corridors and surrounding bars in Brussels are thick with lobbyists seeking to weaken EU privacy laws: they can't fix it at home, so they're trying to tone down the EU end instead.
That would have worked if it wasn't for Edward Snowden...