Can a man take his husband's last name in Vermont?

Yes. In states where same-sex marriage is legally recognized, a certificate of marriage is sufficient proof of legal name change. This is true for drivers licenses, voter registration and other instances controlled by state law. By special policies of federal agencies, a same-sex marriage certificate can be used as proof of legal name change even for your US passport and your US Social Security Card. The federal government will recognize a same-sex marriage certificate ONLY for the purpose of legal name change, since state law controls what your legal name is.

Once you have your new ID, you can change your name with all the public utilities, banks, and other private companies you do business with, including your employer, also showing your marriage certificate to explain the change.

Once you have changed all of your ID, you are free to move to a state where same-sex marriage is NOT recognized, since the new state cannot force you to return to using your maiden name.

Keep in mind that once you have changed your name by marriage, the only way to change it back is by divorce decree or court order.