Why does the Superman #42 Lobo have the Justice League International keyword? I haven't read the whole series, but as far as I've been able to find out, he only appeared in it as a villain, and that only for a few issues.

I wondered that same thing. I have read the whole series -at least, up to Zero Hour - and yeah, he only appears in a few, as a villian. I mean, he pretends to be on their side for a while, so I guess that counts? Apparently?