  A simple criterion is provided how the (anti-)localization properties of
graphene are determined in the presence of inter-valley scattering, Kane-Mele
topological mass term, and Rashba spin-orbit interaction (SOI). A set of
(pseudo) time-reversal operations show that the number of effective internal
degrees of freedom, such as spin and pseudo-spins distinguishing the sublattice
and the valley, is the crucial parameter for localization. It is predicted that
perpendicular electric field due to gate voltage of the substrate drives the
system to anti-localization by enhancing the Rashba SOI.
