Rangers have a way of knowing who has a permit and who doesn't. When five of us day-hiked Shasta from the North, a ranger was waiting on the summit. Only four of us had permits. The ranger busted the guy without a permit, and never even asked the rest of us whether we had them.
Jedi Rangers missed me a few times back in the 90's. They got me good in 99 though - twice in one day. That's what really made me believe in karma and straighten out my permitless ways.
I had some nasty run ins on day hikes when I was farther back than the ranger thought I should/could be, but they always let me continue on. Many times when the hike went bad and we came in late (over 24 hours) I wondered if they would have someone waiting at the trail head, but that's dehydration and sleep deprivation thinking there.
My advice is to always follow the letter of the law. Never mind the spirit of the law though, that's open for interpretation.
.....................................................DUG