orthography - Non-preemptive? Non-pre-emptive? Emptive?

We can describe something as pre-emptive, no issue there.

If something isn't such, how can we write that? Word gives me red squiggles on 'Non-preemptive', but this looks silly with a double hyphenation.

Which leads me to wonder why 'pre-emptive' is hyphenated anyway? 'Emptive' isn't a word, and other 'pre' prefixes aren't hyphenated (e.g. prefix, predecessor).