Wessels will be unavailable for South Africa's upcoming test matches.
Springbok front-rower Wessels faces a suspension of nine matches for touching Josh Murphy's private parts during the Bulls' United Rugby Championship victory over Connacht.
The incident occurred in the 18th minute of the close contest in Galway on Friday, with Connacht forward Murphy receiving a 20-minute red card after responding aggressively by striking Wessels on the head area.
After the Connacht player reported the incident to the match official, the situation was examined by the TMO, who found no definitive proof.
The Bulls player remained on the pitch until he was replaced in the second half of the match.
While the URC confirmed that Murphy's temporary sending-off was overturned by a governing body, the Springbok was found to have violated law 9.27, which specifies:
"Any athlete must not engage in actions that is against the principles of fair play. This includes touching, twisting or compressing the private areas."
The panel were satisfied that the event met the level for dismissal and warranted a 12-week suspension, the shortest ban under World Rugby rules for such an offence.
However, Wessels' ban was reduced by three weeks because of his good conduct prior to and at the proceedings and his good record.
Wessels and the Pretoria-based team are entitled to appeal, but as it stands, the ban will rule the young player out of the Springboks' fall internationals against Japan, Les Bleus, Italy and Ireland.
He will also miss the Bulls' URC games against Glasgow, the Lions and the Cell C Sharks, as well as Investec Champions Cup fixtures with Bègles and Northampton.
Wessels has won ten international appearances for South Africa and was included in their Rugby Championship-winning team during the recent tournament.
The Connacht player, meanwhile, is available to face Munster in this weekend's inter-provincial derby after being exonerated.
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