certain combo's could pass the sniff test without cats. Emissions is mostly about efficency. However almost everywhere requires the cats to be present for the visual portion of the test.
As said above, you won't pass a visual without cats. Usually the fine for getting caught is just a $50 or so fix-it ticket. Probably the best thing to do would be to tack weld heat shields where the cats would go. That's what i'll wind up doing with my car.
In washington we don't have a visual test (at least for my cars) so if you pass the sniffer your golden. Most pre obd II well tuned combos without cams with big overlaps can do it.