You asked the following:

Reuben had maintained a ma’arufia relationship with a group of Christian clerics for many years. Reuben was a rabbinic scholar who taught Torah to the public without accepting payment.

His students became aware of the profit that he earned from his ma’arufia, and they began interfering with the relationship in a manner that caused him financial loss. Reuben complained about them before the community. The community then separated the students from that ma’arufia by placing them under a ban and issuing an ordinance.

The community remained uncertain whether it could also prevent other Jews, who weren’t Reuben’s students, from entering into business with these clerics.

From the wording of your question, it appears that the law of ma’arufia isn’t ordinarily practiced in your community. Since you haven’t previously followed this practice, one individual can’t compel the entire community to adopt a special custom for his benefit alone.

[A ma’arufia was an established commercial relationship between a Jewish merchant and a regular Christian customer, supplier or patron.]