False prophets have nothing to do with canon law. They're a promised obstacle to the Christianity (both Catholics and Protestants - we have our own share of false prophets who call themselves Catholic!)
I'm not sitting here making money and deciding who's saved and who isn't. It's not my competence, nor is it the competence of a hack novelist. But as the DaVince Code so aptly demonstrated, it's easy to take a little truth, mix it with fanciful fiction, and call it "gospel".
Pretty soon, we're drinking Kool Aid and waiting for comet Hale-Bopp to rapture us to the stars...
I don't think that is what Lahaye is doing, at least as I understand him. I tend to think of these things as prompting you to think and examine, not as trying to tell what definitively is or shall be.