On Saturday, Nov. 14, a crowd of hundreds of people filled a park in Salt Lake City to formally resign their membership in the Church of Jesus Christ of Latter-day Saints.

They were responding to news that the church had issued a new set of guidelines regarding gay and lesbian members and their families. The new policy, published in a document called the Handbook of Instruction, says that Mormons in same-sex relationships — cohabiting or married — may face excommunication. Perhaps more important, children living in a household headed by a same-sex couple will not be permitted to join the church until they are 18 and then only if they disavow their parents’ marriage as apostate.

While Mormons are not alone in their resistance to same-sex marriage, their history with the issue is especially contentious — most infamously in 2008, when the church advocated successfully for the passage of California’s Proposition 8, which placed a state constitutional ban on same-sex marriage. However, in recent years Mormon leaders have appeared to soften their stance: The church fought housing and employment discrimination against gay people; a prominent leader and apostle named Dallin H. Oaks spoke out against Kim Davis, the Kentucky county clerk who refused to issue marriage licenses to gay couples; and the church released a public statement and launched a website saying that homosexual attraction is not a choice. That statement seemed to allow more room for gay and lesbian members to participate in Mormon congregations. In light of these moves, the Handbook of Instruction change appears to be such an about-face that some members, both gay and straight, feel forced to resign.

The Mormon General Handbook of Instruction, used by bishops and other lay leaders around the world, is not considered scripture. But over the years, it has become a sort of ad hoc canon law, defining how most Latter-day Saints see and practice their faith. It’s regularly updated, and successive versions have recorded policy shifts on birth control (acceptable, with caveats), divorce (complicated), dietary codes (still strict) and homosexuality (see above). The Handbook of Instruction is a good bellwether for church attitudes, and it powerfully affects how local authorities treat the members in their charge. A change to policy in it is, in other words, a very big deal.

What has caused the most pain is the inclusion in the policy of the children of same-sex couples. They are ineligible for a naming blessing, which holds special emotional and spiritual significance for Mormon families. Baptism into the church at the age of 8 (considered the age of accountability by Latter-day Saints) is also forbidden. Both events are community celebrations, with an entire congregation often taking part. Barring children with gay parents from these rituals looks especially draconian and may mean that children who would otherwise be welcomed into Mormon life will be raised entirely outside the church.

One way to interpret this change is as part of a great retrenching on the part of the LDS Church that has been going on for some time. Mormons have always considered themselves a people apart, the only holders of the true priesthood of Jesus Christ’s restored gospel, as well as long-ago refugees from religious intolerance and violence. Mormon life emphasizes community and family connection. Resistance to secularization, no matter the issue in question, can be seen as a strengthening of the identity that holds Mormons together.

Of course, borders to keep people in necessarily keep others out. Melissa Inouye, a co-director of the Mormon chapter of the Foundation for Religious Diplomacy, writes that the reason so many members of the church are frustrated or disappointed by the change is that “they perceive a conflict between Christ’s charismatic pattern of ignoring religious rules to bless social and spiritual outcasts and the organizational boundary keeping set out in the policy.”