From Longman Dictionary of Contemporary Englishfair gameˌfair ˈgame noun [uncountable] CRITICIZEif someone or something is fair game, it is acceptable, reasonable, or right to criticize them The young star’s behavior made her fair game for the tabloid press.
Examples from the Corpus
fair game• All kinds of birds and fish were also fair game, with parrots being particularly prized prey.• Government officials were always fair game to be bought by special interests.• However, small, non-mechanical parts are fair game and might show considerable savings.• Any woman on this street would seem to be fair game, and especially a gaijin.• The paper seems to think that just because I'm a politician, my entire family is fair game.• Any effect that a change in a gene has on its own replication probability is fair game for natural selection. 