(NBC NEWS) -- The Supreme Court heard arguments about same sex marriage Tuesday, with thousands of supporters and opponents gathered outside.
The case is an appeal of California's Proposition 8, which limits marriage to opposite-sex couples.
Proponents of Prop 8 claimed the original purpose of marriage is procreation.
To that argument, justices took issue.
Justice Kagan asking whether it would be constitutional to ban people over 55 getting married, and Justice Breyer asking whether it would be constitutional to ban people who were sterile from getting married.
Attorneys the same-sex couples who brought the suit argue it's unconstitutional to prevent them from getting married.
Justice Roberts asked why they had to include everyone on the institution of marriage, while Justice Scalia asked about the constitutionality of the ban.
A decision is expected in June.