The legal treatment of autonomous algorithmic collusion in light of its technical feasibility and various theoretical considerations is an important issue because autonomous algorithmic collusion raises difficult questions concerning the attribution of conduct by algorithms to firms and reopens the longstanding debate about the legality of tacit collusion. Algorithmic collusion, namely, direct communication between algorithms, which amounts to express collusion, is illegal. Intelligent and independent adaptation to competitors’ conduct by algorithms with no direct communication between them, which is tacit collusion, is generally legal. There should be ex ante regulation to reduce algorithmic collusion.