Shri Nara,
I think it was Swami Vivekananda who first went to the west and tried to publicise hinduism along with his brand of Yoga called "Raja" Yoga, though Patanjali did not make such classification. Subsequently several guruijis/swamijis found it a very convenient method to take their own brands of "yoga", establish a centre in the west (read U.S.) and lead a life of luxury. None of them patented their yoga. The westerners were quick to grab this marketable commodity and make money out of it from a gullible public. Hence I feel there should be no question, now, of India owning the patent rights for yoga.
What is generally taught in the guise of yoga in the west is Hatha Yoga, I believe which has mainly to do with twisting the body to certain postures for maintaining good health. It does not deal with the yoga which deals with the final liberation, which is the main objective of Yoga Darsana. Such exercises cannot be patented since anyone who looks at a picture or photo of someone else in such a pose can very well try, as long as he is prepared to suffer the after-effects. So, unless people are prohibited from making even such attempts, how can we enforce the patent?