Judaism is not like Catholism in that there is no central authority (Like a Sanhendrin) Its very spread out. The Syrian community is small and very cohesive so they can do things the larger community cannot.
A group like Satmar can throw out someone from Satmar as they are small and cohesive, but they cant throw out someone who is not a Satmar , or who doesnt want to be a satmar.
While you might say there are Gedolim, Many jews do not hold by the Gedolim and mockingly call them ” Supreme Charedi Leaders” Their power and influence and holds to those who follow them, And I stand by my statements until there is a Sanhedrin, you cannot throw someone out from Judaism, they will just go to another group of Jews