Mon Nazir 58 (really 57, we'll say something from yesterday)

R' Huna held that there is an issur to shave the head of a minor, but a woman is permitted, since she's not warned not to cut the hair. R' Ada holds there is no Issur to cut a minor's hair, however, whoever it is Assur to cut their hair, a woman is also commanded not to cut their hair.

Tosfos proves that the Halacha follows R' Huna. Since the Gemara in Bava Metziah that explains usually you cannot make a Shliach for an Aveira. However, a courtyard, which acquires for you objects found in them as if they're your Shliach even for acquisitions that are an Aveira. There is an argument why. One Shita holds because it's forced to do it. We only say you can't have a Shliach that has a choice whether to do it or not. Another Shita holds because the courtyard is not commanded in Mitzvos. You can't make a Shliach that is also commanded in that Mitzvah.

One of the Nafka Minas are making a woman your Shliach to shave the hair of a child. She's not commanded not to shave, but she's doing it on her own will and nobody forced her. So we see that mean are commanded not to shave the child's hair (and we consider this a Shliach for an Aveira) however she's not commanded not to shave the child, despite the fact that men are Chayiv.