Acausal systems are implementable. They're common in signal processing and even in some rather exotic control systems: https://www.researchgate.net/publication

Acausal systems are implementable. They're common in signal processing and even in some rather exotic control systems: https://www.researchgate.net/publication/253627368_Feedforward_control_of_acausal_systems_under_broadband_deterministic_forcing https://www.researchgate.net/publication/253627368_Feedforwa...