Final answer:
John may not be able to enforce the contract with Issac if he is not licensed to practice medicine in Florida, as contracts for illegal activities are usually unenforceable.
Step-by-step explanation:
Whether John will be able to enforce his contract with Issac for medical services rendered in Florida depends on legal principles regarding the practice of medicine and contract enforceability. If John is not a licensed doctor in Florida, providing medical services without a license is generally illegal. Contracts for illegal activities or services are typically considered unenforceable by courts as they violate public policy. Therefore, even if Issac owes John $2000 for medical services, John might not be able to enforce the contract in a court of law because he provided services for which he was not legally authorized in Florida. However, specific circumstances and local laws should be taken into account, and this situation might require the consultation of a legal professional.