KNVB refuses FC Groningen fans from game they were not allowed to see anyway

NOS Football–
The KNVB has penalized FC Groningen with an empty stand at its next home match. This is actually a wash, as the club had previously decided in consultation with the mayor not to allow any spectators at all this season.
The KNVB decided today that Groningen’s Z-side must remain empty Sunday in the premier league match against Sparta Rotterdam. The club will be penalized for the disorderliness at the suspended match against Ajax on May 14.
Smoke bombs were thrown onto the pitch twice from the Z-side already in the opening phase of the match. In addition, a supporter entered the field. According to the protocol of the KNVB, which was drawn up after the tumultuous cup match between Feyenoord and Ajax, these incidents were reason to stop the match permanently.

Supporters throw fireworks on field at FC Groningen-Ajax: game halted
Two days later the game was played out. In an empty stadium Ajax won 2-3.
Series of incidents
Groningen, relegated from the premier league this season, has been plagued by supporter problems in recent months. For example, defender Jetro Willems was slapped by a fan, a supporter entered the field and a young spectator threw a cup of beer against the linesman.
After the latter incident, the game against NEC was also stopped and later played out in an empty stadium.
The KNVB advises Groningen to consider hanging nets to prevent supporters from throwing objects onto the field. Earlier, Feyenoord decided to do just that at De Kuip.
House rules
Groningen reports that it has suffered substantial financial losses, having had to play out the games against NEC and Ajax without an audience and playing against Sparta again in an empty stadium. The club is going to try to recover damages from the spectators who misbehaved.
In addition, Groningen is having a study conducted on how to increase security in the stadium. The club has already announced that it will tighten the house rules. Those who violate them next season can expect a fine of at least 10,000 euros.