Growing instructions I've seen nearly all say to cut back stems and foliage "after they turn yellow". Here in Northern California (Sonoma) the sturdy regal lily stalks don't even think about turning yellow until the new stalks start to push the old ones out. Here, the regals are the first of our lilies to bloom, usually in March or April, and the very last to die back. The old stalks don't even begin to yellow and die back until January. That's a long time to look at stems. Can I cut back earlier, even partially, or do I risk weakening the bulbs?
It is probably the lovely fog in Sonoma that never lets the flowers turn yellow. I'd say, you can cut them safely in the Fall. The cold would have already sent the bulbs into hibernation, by say November 1, if not before, and you could do it then.
If you are still worried, go ahead and just cut a couple of them off, and watch them the next Spring.