 Operator equation in a path integral

An operator equation in a path integral $\mathcal{O}(x)=0$ asserts that insertions of $\mathcal{O}(x)$ vanish in every time-ordered correlation function with the other insertion points separated from $x$. Derivatives of time ordering can produce Ward identity contact terms at coincidence. For example, conservation of a Dirac current gives a vanishing separated-point divergence, while a charged insertion contributes a delta-function contact term fixed by its transformation. A vanishing one-point expectation value alone is insufficient.