Dan's Boss - S3-E7
Continuity mistake: Near the end, when Dan sets the books and folders down to get a salad, the folders on top slide off the books. Dan ends up leaving it as is when he walks away, but in the next shot the folders are back on the books.
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