Copied this from:
http://www.ava.gov.sg/AnimalsPetSector/CITESEndangeredSpecies/Singapore does not allow the keeping of exotic pets such as reptiles, amphibians and primates as pets for the following reasons:
* They may introduce and spread diseases to humans and domestic animals.
* Collection of wild animals for trading will lead to ecosystem imbalance and threaten the survival of endangered species.
* The welfare of the animals may be compromised due to reasons such as unsuitable living conditions, poor diet and pet owner's lack of knowledge of the proper care for the animal.
* Singapore's biodiversity would be greatly affected if such exotic pets were released in the wild, as most of them are non-native.
* If the animal escapes, it may cause nuisance, fear and trauma to the general public.
Some examples of exotic pets include star tortoises, iguanas, tarantulas, snakes, salamanders, slow lorises etc. For a list of pets that are approved to be kept in Singapore, please click here.
Maybe if you really have the tortise interests at heart, you might wish to contact them at the contacts available. Let them know it's an adopted tortise and I don't think they'll pass any charges as long as you declare it and allow them to 'confiscate' it