All Black Williams fined over cocaine
Williams was fined €1 500 (US$1600).
He was sanctioned for "behaviour damaging the image and reputation of rugby, ethics and sports ethics", the French league said in a statement.
Both Williams and O'Connor, who escaped a fine, were ordered to take part in an educational programme for younger players.
The duo were arrested after a police drug bust outside a nightclub near the Champs Elysees in February. They were both fined by police - Williams for buying cocaine and O'Connor for using it.
The 35-year-old lock Williams was in the process of being fired by French Top 14 champions Racing 92 and O'Connor, 26, recently returned to Toulon following suspension.
Agence France-Presse