Agreed. It is a complete none starter as Ashworth would be making an approach on behalf of NUFC, so any restriction would be between NUFC and BHAFC, which as you've pointed out would be a waste of time because we already have the power to refuse another club speaking to our players (unless in the last months of their contract) under FA rules. This would otherwise surely come up every time a manager moves clubs - how would transfer system even work if you ended up with adhoc restrictions between clubs. You got it right, we can just tell them to sling their hook if they want to speak to our players.
Yes of course we have the right to do that. But we all know football doesn't work that way in reality, and players and managers are sounded out long before an approach from a club becomes official. All it takes is for £200k a week to be mentioned to the right agent and suddenly you have a player interested and trying to force a move, and usually the selling club then reluctantly has to negotiate a transfer fee or end up with a p1ssed off player on their books.
Can only think of Spurs recently refusing to sell and Kane has not been the same player since.