law: Indian Contract Act, 1872 
  27. Agreement in restraint of trade,
  
  void
  Every agreement by which anyone is restrained from exercising a
  
  lawful profession, trade or business of any kind, is to that extent void.
   Exception 1 :  Saving of agreement not to carry on business
  
  of which goodwill is sold-One who sells the goodwill of a business may agree
  
  with the buyer to refrain from carrying on a similar business, within specified
  
  local limits, so long as the buyer, or any person deriving title to the
  
  goodwill from him, carries on a like business therein, provided that such
  
  limits appear to the court reasonable, regard being had to the nature of the
  
  business.