The player will be unavailable for the Springboks' fall fixtures.
Springbok prop Wessels faces a suspension of nine matches for making contact with Josh Murphy's genitals during the Blue Bulls' United Rugby Championship victory over Connacht.
The incident took place in the 18th minute of the close contest against Connacht on last Friday, with Connacht forward Murphy being shown a temporary dismissal after responding aggressively by hitting the South African on the head.
Following Murphy reported the incident to referee Mike Adamson, the contact was examined by the TMO, who determined no definitive proof.
The Bulls player stayed on the field until he was replaced in the second half of the match.
Although the URC confirmed that the Irish player's temporary sending-off was overturned by a disciplinary panel, Wessels was found to have breached law 9.27, which specifies:
"A player must not engage in actions that is contrary to the spirit of good sportsmanship. Such behavior covers grabbing, pulling or squeezing the private areas."
The panel determined that the contact reached the red card threshold and justified a 12-week suspension, the minimum ban under World Rugby rules for such an violation.
However, the player's suspension was reduced by 21 days because of his good conduct prior to and at the hearing and his good record.
The forward and the Pretoria-based team have the right to challenge the decision, but as it stands, the suspension will rule the 24-year-old out of the South African national team's fall internationals against the Brave Blossoms, Les Bleus, Italy and Ireland.
He will additionally be absent for the his club's URC games against Glasgow, the Lions and the Cell C Sharks, as well as European cup fixtures with Bordeaux and Northampton.
Wessels has earned 10 caps for South Africa and was included in their tri-nations champion squad over the summer.
Murphy, in contrast, is available to play against Munster in Saturday's inter-provincial derby after being exonerated.
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