The Australian Open ticket conditions of sale and entry prohibit fans bringing “flags, banners, signs larger than 180cm by 90cm in size or with handles longer than 50cm” as well as “unauthorised promotional, commercial, political, religious or offensive items of whatever nature including clothing, banners, signs, symbols, leaflets, stickers or flyers.”
While the size of the flag remains unclear, the Russian flag would likely be deemed an unauthorised political banner with the flag currently prohibited from being used in relation to individial players competing at the event, who cannot represent the country in response to the war in Ukraine.