International clearance is only required for players moving between associations, more or less:
”an International Transfer Certificate (ITC) is required for every player aged 10 years or over … who is not an English national, and is registering for a club in England for the first time, as well as any player who has played under another National Association (including the other Home Associations)
The process of obtaining an ITC ensures that a player, when moving from a club in one National Association to a club in another, is under the jurisdiction and disciplinary powers of the new Association. It is a key element in the registration of a player and ensures that they are eligible to play for their new club, as well as acting as a check to ensure the player is not under contract with their previous club, or subject to any suspension.“