  Hard thermal loops play a central role in the theory of long wavelength
excitations of a quark-gluon plasma. We show in this paper how our recent
derivation of their generating functional from the Dyson-Schwinger equations
sheds light on their semi-classical nature and their remarkable gauge
structure. In particular, we show that our kinetic equations can be written in
terms of auxiliary gauge fields with zero curvature. Remarkably, the latter
property determines entirely the dynamics in the kinematical regime of hard
thermal loops. This explains in particular why the generating functional could
have been obtained by Taylor and Wong from gauge invariance considerations. It
also clarifies the role of Chern-Simons theory in this context.
