According to the official VGC Rules:
Does this mean that Smeargle cannot use any moves that it obtained by Sketch?Pokémon may only use moves that have been learned through one of the following methods:
-By leveling up
-By TM or HM
-As an Egg Move, through breeding
-From a character in the game
-A move already known by a Pokémon received at an official Pokémon event or promotion