Active player

The active player is the player taking the current turn. Unless otherwise specified by the card’s ability, the active player makes all necessary decisions for all card abilities. Whenever multiple effects happen at the same timing point, the active player decides the order in which those effects resolve.

—KeyForge Master Rulebook v17.4 September 2024

Commentary

There are currently no cards that force the non-active player to make any decisions. According to FFG, "The 'unless otherwise specified' language of card abilities was included more for future-proofing purposes in case there was a strange interaction between cards that would instruct the non-active player to make a decision."

Source