law: Indian Contract Act, 1872 
  21. Effect of mistakes as to law
  A contract is not voidable because it was caused by a mistake as
  
  to any law in force in 6[India]; but a mistake as to a law not in
  
  force in 6[India] has the same effect as a mistake of fact.
   7  [* * * ]
   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.