Rule 903.3

Each deck has a legendary card designated as its commander. That card must be either (a) a creature card, (b) a Vehicle card, or (c) a Spacecraft card with one or more power/toughness boxes. This designation is not a characteristic of the object represented by the card; rather, it is an attribute of the card itself. The card retains this designation even when it changes zones. Example: A commander that’s been turned face down (due to Ixidron’s effect, for example) is still a commander. A commander that’s copying another card (due to Cytoshape’s effect, for example) is still a commander. A permanent that’s copying a commander (such as a Body Double, for example, copying a commander in a player’s graveyard) is not a commander.