  Observing charge-parity (CP) or time-reversal (T) violations in the leptonic
sector will give useful information to elucidate the nature of neutrinos.
CP-violating couplings in charged leptonic currents carry out the weak phases
necessary to break these symmetries. Here we study the interference of
$W^{\pm}$ and $H^{\pm}$ bosons mediated amplitudes as the origin of possible CP
and T violation in semileptonic decays of $K^{\pm}$ mesons and $\tau^{\pm}$
leptons. We use the experimental bound on the T-odd transverse polarization
asymmetry in $K^+_{\mu 3}$ decays to predict an upper limit on the CP violating
effects in $\tau \to K \pi \nu$ decays. In the framework of this model with
scalar-mediated interactions, we find that current limits on the former process
indicate that the CP violating effects in the latter are much smaller than the
limits reported so far.
