Proposed FIFA regulations for football agents, including a fee cap, are incompatible with British competition law, an English FA tribunal ruled on Thursday after a five-month arbitration.
The tribunal was set up in June when agencies CAA Base, Wasserman, Stellar and ARETE challenged the implementation of FIFA's new regulations in the National Football Agent Regulations (NFAR) for English domestic transfers.
The regulations limit an agent's fee to 3% when a player's annual salary is more than $200,000, and 5% when it is under that amount.
The limit doubles for an agent representing both the player and the club in a transfer.
"The FA Rule K Tribunal... declared that if the FA implements the fee cap and the pro rata payment rules in the NFAR, it will be in breach of the Competition Act 1998," the FA said in a statement.
"The FA is considering the implications of the decision and will provide a further update as soon as it is able."
Earlier this year courts in Germany and Spain issued temporary injunctions against implementing some of the regulations in domestic transfers.
The FA tribunal's decision only affected two of the multiple provisions in the regulations, FIFA said in a statement.
"Other key provisions were endorsed by the tribunal, including those preventing agents from representing multiple clients in a transfer, and requiring that the client pays the agent, both of which were unsuccessfully challenged by the agents.
"FIFA has already scheduled a meeting with the Football Agent Working Group to discuss the outcome of these proceedings," FIFA added.
A statement from the four agencies leading the legal challenge (CAA Base, Wasserman, Stellar and ARETE) said FIFA's proposed rules would have a "devastating effect" on football agents.
"Our case aimed to protect hard-working, trusted agents from going out of business, leaving players vulnerable. We are pleased that the tribunal agreed that FIFA's rules relating to a fee cap are unenforceable from a UK competition law perspective," the statement added.
"Agents are not against regulation. However, as we proved to the Tribunal, there are serious concerns about the way in which FIFA’s proposed rules have been introduced, including how they affect not just agents, but players and clubs too.
"We hope that legal proceedings in Europe will come to the same conclusion to protect agents and the wider football industry from FIFA's overreaching authority."
FIFA won a challenge against its agent regulations in July when the Court of Arbitration for Sport (CAS) dismissed a case brought by a Switzerland-based agents' association.