Within two Higgs doublet models, it is possible that the current vacuum is
not the global minimum, in which case it could possibly decay at a later stage.
We discuss the tree-level conditions which must be obeyed by the most general
scalar potential in order to preclude that possibility. We propose a new
procedure which is not only more general but also easier to implement than the
previously published one, including CP conserving as well as CP violating
scalar sectors. We illustrate these conditions within the context of the Z2
model, softly broken by a complex, CP violating parameter.Comment: RevTex, 13 pages, 3 figure
