2,865. Can a Non-Jew Become a Nazir?
Hilchos Nezirus 2:15
If the son doesn’t want to be a nazir and he objects, if his family objects, if he cuts his hair or his family cuts his hair, thereby demonstrating that either he or his family doesn’t want him to be a nazir, then he’s not a nazir. A father can impose a nazirite vow on his son until he reaches the age of majority.
Hilchos Nezirus 2:16
Nazirite vows do not apply to non-Jews as per Numbers 6:2: “Speak to the children of Israel….”