Asset ownership and other rights vary from state to state. However, some general concepts apply to all states in regard to marriage, death, ownership and rights. Concepts are also similar from state to state regarding contracts, wills and estates and divorce.
Once a marriage is dissolved, the former spouses generally have no further obligations or rights vis-a-vis one another, except for those specified in a divorce decree. The decree is a court order. It may, for example, order one spouse to relinquish property to another, confer visitation rights of children, or order support payments from one to the other. Sometimes a subsequent marriage can trigger the decree. For example, the decree might say support may end if one former spouse gets remarried.
In most circumstances, a second wife's rights are the same as if she were a first wife, excluding any orders in the the divorce decree of the first marriage. Rights altered by the decree aside, marriage usually confers upon the second wife special rights she would not have if she was not married to her husband, but only cohabiting or dating. These special rights to the assets of a spouse can be contractually eliminated by pre- or post-nuptual agreements. They can also, in effect, be precluded by a divorce decree that a spouse cannot transfer an asset that doesn't fully belong to spouse. Unless altered in some fashion, a first or a second wife will have at least some special rights related to the death of her spouse.
A will is a special kind of legal document. It is not a contract; two parties are not agreeing to something. A will is a document recognized by probate courts as a binding legal document clarifying the wishes of a person. Wills usually include the intention or "will" of a person regarding his or her assets. Wills cannot supersede state or federal laws, and they do not supersede court orders. However, in the absence of a state law or court order, such as a divorce decree, a will is executed according to the deceased wishes. So long as a will is legal and not in violation of any laws or contracts, it will supersede the wishes of a spouse.
Marriage is legally recognized in all states, as are wills and contracts. There is a pecking order to what laws supersede others and what legal instruments supersede others. Generally the sequence, highest to lowest, is: federal law, state law, court orders, marriage, contracts. However, agreements of all kinds can be made separately from rights conferred by law, by marriage or even by other contracts. A spouse cannot take on rights that belong to others or are the jurisdiction of others, but she can relinquish them through a contract, as can a husband.