Final answer:
In a legal context, George may refuse Albert's services if the contract demands the personal service of John Jones; otherwise, George's refusal could constitute a breach of contract. The specific terms and nature of the roofing services outlined in the contract are critical in determining the legality of the refusal.
Step-by-step explanation:
In the scenario described, John Jones enters into a contract with George Hopkins for roofing work, and afterward decides to subcontract the work to Albert. When Albert arrives to complete the job, George refuses to allow him to do the work. This situation centers around concepts of contract law, specifically delegation of duties and potential breach of contract. If the contract explicitly or implicitly required the personal services of John Jones, then George may have the right to refuse services from Albert. In absence of such terms, refusing Albert's services might be a breach on George's part. The specifics of the contract and the exact nature of the roofing services will be key in determining the legality of George's refusal and the potential remedies available to John Jones.