Constantin's assault of former Swiss national team coach and current TV pundit Rolf Fringer on September 21st also earned him a 100,000 Swiss franc fine.
"The violent behaviour of Christian Constantin against Rolf Fringer, which (Constantin) doesn't deny, is clearly a violation of the rules of conduct", the SFL's disciplinary committee said in a statement.
The SFL said Constantin was prohibited from entering all football related venues during the ban, including for Super League and national team events.
Video captured at the match in Lugano, which Sion won 2-1, shows Constantin striking Fringer while he is already on the ground.
The slap forces Fringer to fall further backward before Constantin walks away and fixes his watch.
Fringer, who managed the national club in the 1990s, told Swiss media that Constantin had in fact struck him several times before the blow that was caught on tape.
The controversial Sion president, who has previously been sanctioned attacking a referee, can appeal the decision.
His son Barthelemy, who is the director of sport at Sion, is also under investigation over possible misconduct.