Are there any places in the Maldives in which we can legally camp?
It is possible but not formally allowed. You have to ask for permission as a favor and then maybe you are allowed
Camping Approval: Camping is possible, but not formally allowed, only as a favor with no guarantee, depends on how many people, days, and how you ask - best to go and negotiate directly with the Island Chief."
You should search and talk with this "Island Chief" but I dont know how and if at the end will be allowed. Anyways I will expect that it is not alowed due to the amount of tourism. Good Luck!
You must provide a proof of accommodation/reservation to immigration upon arrival in the Maldives. If you do not have they might forbid you to enter the country.
The resorts will not allow you allow you to enter their island without having a room booked.
The local islands (where locals live ) might allow you to plant your tent but you will first need the authorization from the island chief.