>Official guidance from the International Civil Aviation Organization, or ICAO, which signatory nations use to create their own regulations, did not say what to do if TCAS and ATC issued conflicting avoidance instructions. Similarly, European regulations failed to cover this scenario.

Technical in the sense of giving priority one over the other; the priority was clear in the US but at the time not strictly set in Europe or Japan (a near miss happened one year before because of conflicting instructions) and in Russia the opposite (highest priority ATC) was true with TCAS being a new thing obligatory for flights to Europe, of the five crew members only one pilot seemed to be aware that the two TCAS are tightly coordinated (CLIMB/DESCEND) for a last resort, but nobody listened to him.