  't Hooft's derivation of quantum from classical physics is analyzed by means
of the classical path integral of Gozzi et al.. It is shown how the key element
of this procedure - the loss of information constraint - can be implemented by
means of Faddeev-Jackiw's treatment of constrained systems. It is argued that
the emergent quantum systems are identical with systems obtained in [Phys.Rev.
A 71 (2005) 052507] through Dirac-Bergmann's analysis. We illustrate our
approach with two simple examples - free particle and linear harmonic
oscillator. Potential Liouville anomalies are shown to be absent.
