Premier League clubs including West Ham have moved to block Newcastle United from making lucrative sponsorship deals in an emergency stakeholder meeting on Monday.
The clubs have passed a temporary amendment banning commercial opportunities involving pre-existing business relationships, known as related party transactions.
These deals cannot now be made for the next three weeks, with clubs intent on passing more lasting measures in the meantime through the creation of a working party.
Newcastle believe that the rule is anti-competitive, backed up by their own legal advice, and could be unlawful.
This includes every club in the league except for Manchester City. They are believed to have abstained based on strong legal advice that the vote was unlawful and would see the league acting as a cartel. The Abu Dhabi owned club have been accused of benefitting from related party transactions in the past.
The Premier League will look to make the rule permanent. Any change of Premier League rules votes require 16 clubs to agree in favor.