Wessels will be unavailable for the Springboks' fall fixtures.
South Africa prop Wessels has received a ban of nine matches for grabbing opponent Josh Murphy's private parts during the Bulls' URC victory over the Irish province.
The altercation happened in the 18th minute of the close contest against Connacht on Friday, with Connacht forward Josh Murphy receiving a 20-minute red card after reacting angrily by hitting Wessels on the head area.
After the Connacht player complained to the match official, the event was checked by the TMO, who determined no definitive proof.
Wessels remained on the field until he was replaced in the second half of the match.
Although the URC confirmed that Murphy's temporary sending-off was rescinded by a governing body, Wessels was deemed to have breached the code of conduct, which declares:
"Any athlete should not do anything that is contrary to the principles of fair play. Such behavior covers touching, twisting or squeezing the private areas."
The panel concluded that the event reached the level for dismissal and justified a 12-week suspension, the shortest ban under World Rugby rules for such an offence.
Nonetheless, Wessels' suspension was shortened by 21 days because of his cooperative behavior prior to and at the proceedings and his clean disciplinary history.
Wessels and the Bulls are entitled to appeal, but as it stands, the suspension will prevent the young player out of the South African national team's fall internationals against the Brave Blossoms, France, Italy and Ireland.
He will additionally be absent for the his club's league matches against Glasgow, the Emirates Lions and the Sharks, as well as Investec Champions Cup games with Bordeaux and Saints.
The prop has won ten international appearances for South Africa and was included in their Rugby Championship-winning team over the summer.
The Connacht player, in contrast, is eligible to play against the Irish rivals in Saturday's inter-provincial derby after being exonerated.