He entered into a "digital art" category and used a tool available to digital artists. If they wanted him to only tools such as Photoshop or a Wacom tablet, the

He entered into a "digital art" category and used a tool available to digital artists. If they wanted him to only tools such as Photoshop or a Wacom tablet, the onus is on the judges to outline that as part of the rules. It would be like having a cake making competition — if you don't want people to use ready-made royal icing or marzipan, you specify that all elements need to be made from scratch.