Actually, if my memory serves me well, ICAO Doc do state in one document that a pilot SHALL follow an ATC clearance unless in emergency , while in another that he SHOULD follow a RA. I do not recall having seen a RA defined as an emergency in ICAO papers....
On the Skyguide/ German authorities issue, if the info we saw is correct , it was a delegation of ATS sevices, not a delegation of airspace . I am not a legal adviser but if this is correct then the Germans are the one ultimely responsible.
as I said ealier, the lawyers are going to have a amazing day ......unless as it was suggested, they all settle things out of court(s) and there is never any trial.....