The lee-bower who claimed starboard
The situation
Crossing on port, Red tacks onto starboard right on the lee bow of an oncoming starboard-tack boat, Green. Green has to luff hard to miss Red's transom as Red settles. Red protests Green — “You're windward now, you have to keep clear of me!”
Once Red completes onto starboard she's the leeward boat and Green is to windward — so windward Green should have kept clear, and Red's protest looks solid.
The question
Is Red right that finishing the tack made her the right-of-way boat?
The ruling
No — Red is penalized. While she was tacking, from head to wind until she reached a close-hauled course, rule 13 made Red keep clear of Green; Green's forced luff happened inside that window, so Red broke rule 13. And even after she settled, rule 15 required her to give Green room to keep clear of the right of way she'd just acquired. The instant of becoming leeward did not erase the foul committed mid-tack.
Completing a lee-bow doesn't backdate your rights — you owe room the whole way through the tack (rules 13 and 15).
Opens the situation on the boat-length grid — scrub it and see exactly how the boats meet. Free, no account needed.
Rules cited
See the underlying rule: Rule 13 — While Tacking.