  We compute the photon asymmetry $B_\gamma$ for near threshold parity
violating (PV) pion photoproduction through sub-leading order. We show that
sub-leading contributions involve a new combination of PV couplings not
included in previous analyses of hadronic PV. We argue that existing
constraints on the leading order contribution to $B_\gamma$ -- obtained from
the PV $\gamma$-decay of $^{18}$F -- suggest that the impact of the subleading
contributions may be more significant than expected from naturalness argumen
