The player will be unavailable for the Springboks' fall fixtures.
South Africa front-rower Wessels has received a ban of nine games for making contact with opponent Josh Murphy's genitals during the Blue Bulls' URC win over Connacht.
The incident occurred in the 18th minute of the Bulls' 28-27 win in Galway on Friday, with opposing player Murphy receiving a 20-minute red card after striking back by hitting the South African on the head area.
Following Murphy complained to the match official, the contact was checked by the TMO, who concluded no conclusive video evidence.
The Bulls player remained on the field until he was replaced in the second half of the game.
Although the URC confirmed that the Irish player's temporary sending-off was rescinded by a governing body, the Springbok was found to have breached the code of conduct, which states:
"Any athlete should not do anything that is contrary to the spirit of good sportsmanship. Such behavior covers grabbing, twisting or squeezing the private areas."
The panel concluded that the contact reached the level for dismissal and justified a 12-week suspension, the minimum ban under World Rugby rules for such an violation.
However, the player's ban was reduced by 21 days because of his good conduct prior to and at the hearing and his clean disciplinary history.
Wessels and the Pretoria-based team are entitled to challenge the decision, but as it stands, the suspension will prevent the young player out of the Springboks' autumn Tests against Japan, Les Bleus, Italy and Ireland.
He will also miss the Bulls' URC games against Warriors, the Lions and the Cell C Sharks, as well as European cup games with Bègles and Saints.
Wessels has earned ten international appearances for the Springboks and was part of their tri-nations champion team during the recent tournament.
Murphy, in contrast, is eligible to play against the Irish rivals in Saturday's domestic clash after being cleared.
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