ECS architecture & the state machine

I've recently been learning ECS and getting my head around DoD methodology, one question I have is around a State Machine replacement. ---------- Imagine I have a realtime hack 'n' slash with a series of AI-driven monsters all running around independently. Now imagine the player opens up an inventory - with the desired effect of pausing the monsters behaviour. How would one architect this in ECS? ---------- Do we give the monsters behaviour component a "paused" attribute and iterate through all of the monsters in the game setting it? Or...?