  In a general two-scalar-doublet model without fermions, there is a unique
source of CP violation, $ J_1 $, in the gauge interactions of the scalars. It
arises in the mixing of the three neutral physical scalars $ X_1 $, $ X_2 $ and
$ X_3 $. CP violation may be observed via different decay rates for $ X_1
\rightarrow H^+ W^- $ and $ X_1 \rightarrow H^- W^+ $ (or, alternatively, for $
H^+ \rightarrow X_1 W^+ $ and $ H^- \rightarrow X_1 W^- $ --- depending on
which decays are kinematically allowed). I compute the part of those
CP-violating decay-rate differences which is proportional to $ J_1 $. The
CP-invariant final-state-interaction phase is provided by the absorptive parts
of the one-loop diagrams. I check the gauge invariance of the whole
calculation.
