Rule 109.4 · Objects
Only objects on the stack or on the battlefield have a controller. Objects that are neither on the stack nor on the battlefield aren’t controlled by any player. See rule 108.4. There are six exceptions to this rule:
Subrules
The controller of a mana ability is determined as though it were on the stack. See rule 605, “Mana Abilities.”
A triggered ability that has triggered but is waiting to be placed on the stack is controlled by the player who controlled its source at the time it triggered, unless it’s a delayed triggered ability. To determine the controller of a delayed triggered ability, see rules 603.7d–f. See also rule 603, “Handling Triggered Abilities.”
An emblem is controlled by the player who puts it into the command zone. See rule 114, “Emblems.”
In a Planechase game, a face-up plane or phenomenon card is controlled by the player designated as the planar controller. This is usually the active player. See rule 901.6.