Ozzy tweeted (exed?) that Kanye requested to sample War Pigs. Ozzy denied the sample calling out Kanye as antisemitic. But Kanye sampled it anyway without permission. So I guess lawyers will get involved.
Original now deleted tweet said War Pigs. Now the new tweet says Iron Man. Either way, sample with permission and give credit where it's due. Sampling itself is a touchy subject, I mean search for Moby and his sampling woes. And Kanye has had issues with sampling in past.
All rockstars are involved in controversy, but nobody seemed to welcome it like Ozzy Osbourne. His interview with Night Flight in 1982 is the pinnacle of this.