Businessman preventing two people from transacting a sale on his property
Q: Could mufti advise on the following:
Person A owns a Cash n Carry, person B and person C both are his customer's and purchase from him. At the premises of person A, person B and C meet and start transacting on person A's premises. Person A in turns tells Person B that person C is my customer and you cannot supply him.
1. Is this type of clause permissable in shariah where person A stops person B from supplying person C as he feels it's his customer.
2. If person B and C transacted on person A's property, is the sale valid.