I would agree if this person had not stated that Sharia is above US law.
If it is a moral or religious matter...who cares? But it doesn’t appear to be the case.
As long as it is voluntary, they have no power and no party can be completed to attend or punished.
The city will lose in a real US Court.
People forget that islam goes beyond religion just as their courts will. It will easily turn into intimidation and gang activity.