Historical Rules · 8 July 2022
Rule 109.4b
Official source text from the 8 July 2022 Rules release
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.”