Melamine occurs in minute quantity in food stuffs.
As melamine is not known to be added to food stuff before and it should not be used in food production.
There is not a standard because of " previously believed of low toxicity " of melamine and its rare occurence in food.
There has never been large scale " contamination ".
Only the Pet Food incident arouse the awareness of deliberate adding this chemical in food stuff.
So what is the point of making statutory rules when something is not expected to added ?