As a doctrinal principle, based on the scriptures, the Church affirms that marriage between a man and a woman is essential to the Creator's plan for the eternal destiny of His children.
Sexual relations are proper only between a man and a woman who are legally and lawfully wedded as husband and wife. Any other sexual relations, including those between persons of the same gender, are sinful and undermine the divinely created institution of the family. The Church accordingly affirms defining marriage as the legal and lawful union between a man and a woman.
See Handbook 1 (Section 17.3.10); Handbook 2 (Section 21.4.10).
Now, compare the above with the statement in the last version (2006) of the Handbook (the words in bold are those omitted from the more recent version above):
Marriage between a man and a woman is ordained of God. The Church accordingly opposes same-gender marriages and any efforts to legalize such marriages. Church members are encouraged "to appeal to legislators, judges, and other government officials to preserve the purposes and sanctity of marriage between a man and a woman, and to reject all efforts to give legal authorization or other official approval or support to marriages between persons of the same gender." (First Presidency letter, Feb. 1, 1994).
As a doctrinal principle, based on the scriptures, the Church affirms that marriage between a man and a woman is essential to the Creator's plan for the eternal destiny of His children. The powers of procreation are to be exercised only between a man and a woman who are lawfully wedded as husband and wife.
Any other sexual relations, including those between persons of the same gender, undermine the divinely created institution of the family. The Church accordingly favors measures that define marriage as the union of a man and a woman and that do not confer legal status on any other sexual relationship.
While opposing same-gender marriage, the Church reaches out with understanding and respect to individuals who are attracted to those of the same gender.
See Handbook Book I (pp. 187-88).
Note also that the new statement removes the "powers of procreation" clause from the old version, probably in recognition that many marriages do not involve "procreation" for one reason or another.