It will not be advisable to make transactions in bitcoin within a country where cryptocurrency transactions are illegal by the law. But Imagine this scenario that someone has been using their bitcoins for transaction secretly successfully, and then one day decides to use the bitcoin that they have to make payment for something like a property to the owner of the property, If there is this kind of problem for instance where the owner of the property decides to claim that they did not receive any money in bitcoin, and the case is taken to a law court, what do you think the outcome of the case will be?
If proofs of payment are provided but in cryptocurrency, do you think the court will consider it even though transactions are tagged illegal with it? or will the case be thrown out and the owner of the property with the false claim of not receiving the money be allowed to go freely?
Thisjis a funny scenario and I don't think it can be attempted anywhere. Once something is banned in a country, there is no way the government will want to hear anything about it because it can be seen as a big offense. Reporting such a case to the police can even make the person that make the transaction to end up in jail. For cryptocurrency to be banned in a particular country, I believe their is a penalty for such a person and the government would not want to look into such a matter because it compromised the law that is guiding every citizens of such country. If something like this ever happens, the government can investigate the matter and send the both patties to prison for this.