  We use Lagrangian effective field theory techniques to construct the
equations of motion for an ideal relativistic fluid whose constituent degrees
of freedom have microscopic polarization. We discuss the meaning of such a
system, and argue that it is the first term in the EFT appropriate for
describing polarization observables in heavy ion collisions, such as final
state particle polarization and chiral magnetic and vortaic effects. We show
that this system will generally require non-dissipative dynamics at higher
order in gradient than second order, leading to potential stability issues
known with such systems. We comment on the significance of this in the light of
conjectured lower limits on viscosity.
