Rule 903.9 · Commander

If a commander is in a graveyard or in exile and that object was put into that zone since the last time state-based actions were checked, its owner may put it into the command zone. This is a state-based action. See rule 704.

If a commander would be put into its owner’s hand or library from anywhere, its owner may put it into the command zone instead. This replacement effect may apply more than once to the same event. This is an exception to rule 614.5.

If a commander is a melded permanent or a merged permanent and its owner chooses to put it into the command zone using the replacement effect described in rule 903.9b, that permanent and each component representing it that isn’t a commander are put into the appropriate zone, and the card that represents it and is a commander is put into the command zone.