Responsa על ויקרא 19:14

For we cannot say that the prohibition on the medium and the wizard derives from, “Before a blind person, do not place an obstacle” (Lev. 19:14), which is Rabbi Yishmael’s position in the chapter Arba Mitot (Sanhedrin 56b), about the Children of Noah [non-Jews], that they are prohibited from magic, since we do not rule in favor of R Yishmael {I think this is actually referring to R Yosi}