Legally getting married typically only applies to same sex couples. However also adopted by those who support same sex marriage. It is also used for couples who are now having a legal ceremony, whereas prior only had a nonlegal ceremony.
After unit section 3 of The Defense of Marriage Act (DOMA) was ruled unconstitutional in 2013, this type of ceremony has become increasingly popular.
We are Getting Legalled. You are invited to attend the ceremony at x place at x time. Please RSVP by x date.