21. Effect of mistakes as to law.—A contract is not voidable because it was caused by a mist ake as to any law in force in 1[India]; but a mistak e as to a law not in force in 1[India] has the sa me effect as a mistake of fact. 2* * * * *
Illustration A and B make a contract grounded on the erroneous belief that a particular debt is barred by the Indian Law of Limitation : the contract is not voidable. 3* * * * *