There is one case in particular that has clearly established in case law a right that most of us believe we had all along: the right to simply resign from a church. A second case is important to establish the church's vulnerability to lawsuits when they refuse to honor resignations.
GUINN V THE CHURCH OF CHRIST OF COLLINSVILLE
Final decision by the Supreme Court of Oklahoma, January 1989
Marian Guinn, a member of the Church of Christ of Collinsville, OK, hand delivered her resignation to the minister after he told her he was going to excommunicate her for fornication. The minister refused to honor the resignation, went ahead with the 'excommunication' and then announced it from the pulpit. Guinn sued and was awarded $390,000. On appeal the Oklahoma Supreme Court ruled that Guinn's resignation was effective immediately and that anything the church or the minister did after the minister received Guinn's resignation was tortable. In other words, she could sue for anything they did after she resigned. The court ruled that with her resignation Guinn withdrew her consent to being treated as a member and she withdrew her consent to being subject to church discipline.
Of extra importance is the fact that the court ruled that the right to freedom of religion also includes the right to unilaterally resign from a church.
In several subsequent court cases the Mormon church has agreed to the principles established in Guinn. They have not even attempted to argue that the principles do not apply to them.
THE NORMAN HANCOCK LAWSUIT (Mesa AZ 1985)
In 1985 the Mormon church 'excommunicated' Norman Hancock AFTER he submitted a letter of resignation to the church. Hancock filed an $18 million lawsuit against the church, saying a person has a right to voluntarily resign from a church. The suit was settled out of court and the settlement was sealed. An account on line reports that Hancock filed the suit himself, without the aid of a lawyer, after studying the Guinn case. The same account says that church lawyers started discussing with Hancock just how much money he wanted, but he told them he didn't want their money, that what he wanted was to have his name cleared. Church representatives agreed to change the records such that there would no longer be any record of an 'excommunication': the records would show that he resigned (that he asked for 'name removal').
The Hancock case shows that the church is willing to settle out of court when someone sues because the church 'excommunicates' them after they've resigned their membership. There were some defamation issues in the Hancock case that do not apply to most other cases, however.
The Guinn and Hancock cases were the end of the era when the church told members that there was no way to stop being a member except by excommunication. The church began having a process it calls 'name removal'. However, the church still tells bishops and stake presidents that a member who is 'transgressing' should not be allowed to resign, that "name removal should not be used as a substitute for church discipline". If you've paid attention to the Guinn case, you already know that the church is wrong about that and they can be sued for 'excommunicating' someone who already resigned. At church headquarters they know this very well and they will usually put a quick halt to 'discipline' proceedings if they find out that the former members knows what his or her rights are.
The sample resignation letter available on this site, through the wording that is used, lets the church know that the person who sent it in knows what his or her rights are. Only rarely do they threaten to 'excommunicate' people who've used that letter. Even in cases of blatant 'transgression' the church usually just lets people go.