Esteban Alvarado deflected the attack Wednesday but was given a red card for kicking the supporter in anger immediately afterward.
Alkmaar’s team left the field in protest and the game was halted in the 36th minute. Ajax was leading 1-0.
The soccer association rescinded the red card Thursday, saying Alvarado’s reaction was triggered by the unprovoked attack on him. But the federation added referee Bas Nijhuis was acting according to the rules when he sent the goalkeeper off.
The federation said Alvarado’s reaction “will not result in a ban.”
The federation said Thursday it will decide soon whether Wednesday’s match should be replayed, resumed, or have Ajax declared the winner.
The 19-year-old supporter is in police custody along with 25 others arrested in disturbances during and after the match.
Ajax director Jeroen Slop said the supporter had already been banned from the stadium for a year because of a previous run-in with security guards, but managed to sneak into the cup match with a ticket purchased by a friend. Ajax has changed the sanction to a lifetime ban from all Ajax matches.
Slop apologized for the security lapse, and he said AZ had accepted the apology.
In a rare move, the country’s justice minister Ivo Opstelten got involved in the debate, saying the attack was “beastly” and that “jerks and nuts don’t belong on the field.” He added that he thought Alkmaar coach Gertjan Verbeek was right to walk out under the circumstances.
“I have a lot of respect for how he acted,” Opstelten said. “Intervene immediately, that warms my heart.”
The Dutch players’ union had demanded that the red card be retracted.