A fifth positive test for Melatonium since added to WADA's Prohibited list on 01/01/2016 . You have to worry about how widely and clearly these changes are communicated to athletes. Or is the case of the substance being long acting in the body - So in effect could have been taken three months ago when legal but lingers in the system. Are WADA getting positive tests by stealth.
Surely there would have to be a period of grace following a rule change?