Continuity mistake: While in the courtroom Bull walks up to Christine, Dan, and Harry. The shot changes and he walks up to them again.
Continuity mistake: After the first courtroom scene people are walking out. The right door is open and the left closed. The shot changes and now the right is closed and the left is open.
Answer: Being declared legally dead is called "death in absentia", meaning there is no evidence of death (i.e. a body), but the individual is presumed dead. This can happen to anyone, not just MIA soldiers. If a spouse petitions the courts to grant a divorce on the presumption of death and all criteria are meet, they are legally divorced and free to remarry. The return of the presumed dead would not change the divorce ruling. However, if a spouse does not go through the legal steps prior to remarrying, then the return of the presumed dead spouse would nullify and void the 2nd marriage immediately (and the remarried spouse could face bigamy charges).
Bishop73