It is actually up to each competition, not even each union, to have a Disciplinary Committee. But those judiciary structures roll up for appeal purposes. So for my location in North America, our union DC rolls up to the USA Rugby DC, which rolls up to Rugby Americas North DC, which rolls up to World Rugby. The same is true for Faz - the RFU rolls up to Six Nations Rugby, which I believe then rolls up to WR.
Oh thank the lord the judiciary system has seen some sense. Yay for him, yay for Faz
ETA after RTFA:
“Having acknowledged mitigating factors including his exemplary previous record, immediate apology and remorse, and noted the absence of any aggravating factors, the committee reduced the six week entry point by three weeks,” Six Nations Rugby said in a statement.
Immediate apology and remorse? WHAT? Did they watch the replay? He just couldn't help yelling at the ref. Paul Williams is far more nonchalant then I would have been. I might've shown him the red right there.