The “gauge principle”, a top-down, classical-geometrical principle which has ruled particle theory for over 60 years, is foreign to QFT. Looking back, a flaw — the unavailability in conventional QFT of a Hilbert space framework for massless particles — was elevated into a doctrine. By now, bottom-up, inherently quantum principles for the construction of interactions deserve their place in the sun. Modular localization and the theory of string-localized fields reinforce the contention that local symmetry emerges directly from quantum theory, but global gauge invariance remains in general an unwarranted assumption, to be examined case by case. Armed with those modern tools, we reconsider the classical Okubo– Marshak argument on the non-existence of a “strong CP problem” (thus of a standard axion) in quantum chromodynamics.