Rules Question on Protection & Attacking The Next Round

I am sure that this happens all of the time, but I had no idea how to respond when the players rules question made absolutely no sense.

Someone swings with the Prophet or some other multicolored creature

Blocked by Soldier of the Pantheon

and then it is stated that the Prophet cannot attack next round because she was blocked by a creature with protection last round.

So basically a rules question around something that is not in the rules to my knowledge...as a judge, I have learned the fine art of the slow down, the trigger review, the rule review, the threat of the stack--all classic judge moves to help players arrive at the right decision on their own--my goal as a judge, by the way...

But what does one do when one player is kind of making up weird rules that do not really fit?