What is an annulment?
Formally called a "declaration of nullity," an annulment is a finding by a church court such as the Tribunal of the Diocese of Rochester that a marriage celebrated according to appropriate church law was lacking an essential element — such as the psychological capability of both spouses to assume essential marital obligations — required for a valid marriage and/or that the marriage suffered from a non-dispensed impediment. An impediment to marriage is a circumstance — such as one or both parties being under age 16 — that would preclude marriage; Catholics may ask their diocesan bishops to dispense, or give exemption to, impediments under church law.
Does an annulment make the couple’s children illegitimate?
No. The children of any marriage presumed to be valid when it takes place are legitimate, even if the marriage is later declared invalid.
Does divorce bar a Catholic from the Eucharist?
No. Civil divorce alone does not prohibit one from receiving the Eucharist. However, unless a former spouse has died, a Catholic who has remarried outside of the laws of the church should consult with his or her pastor or pastoral administrator regarding restrictions on participation in the sacramental life of the church.
Sources: Father Louis A. Sirianni; Diocese of Rochester (www.dor.org/index.cfm/tribunal/annulment-faq)