[gen220]

According to the article, there were actually conflicting guidelines.

The FAA said always follow TCAS ("any guidance from TCAS overrides guidance from ATC"), whereas other regulators were either vaguely non-committal to which had overriding priority or assigned priority to ATC.

It also notes that the Russian pilots were not accustomed to TCAS (which was not common in Russia, at the time). Even further, to the extent they were familiar with it, Russian regulations noted that the ATC's guidance superseded all other guidance systems.

[avar]

What the FAA had to say on the matter isn't relevant, and doesn't contribute to there being "conflicting guidelines". The FAA doesn't regulate European airspace.

[gen220]

Sorry, I didn't mean to suggest that the pilots were operating under conflicting regulatory guidances.

Rather, I was pointing out that the international community of aviation regulators had established conflicting norms with regards to the requirement and prioritization of TCAS at the time of the incident.

The conflict in norms was a contributing factor to the incident discussed in the article, and in the aftermath of the incident, those norms were appropriately corrected. The mention of the FAA is relevant because their original guidance (TCAS guidance supersedes ATC guidance) was what the ICAO adopted in response to this incident.