Following the Supreme Court's decision to legalize same-sex marriage nationwide on June 26, the Church released a statement on the ruling:
"The Church of Jesus Christ of Latter-day Saints acknowledges that following today's ruling by the Supreme Court, same-sex marriages are now legal in the United States. The Court's decision does not alter the Lord's doctrine that marriage is a union between a man and a woman ordained by God. While showing respect for those who think differently, the Church will continue to teach and promote marriage between a man and a woman as a central part of our doctrine and practice."
The Church position and doctrine on marriage can be found at newsroom.churchofjesuschrist.org/article/supreme-court-decision-will-not-alter-doctrine-on-marriage.