On the Legal Side: The Convention on the Elimination of All Forms of Discrimination Against Women

"...the full and complete development of a country, the welfare of the world and the cause of peace require the maximum participation of women on equal terms with men in all fields "

The Convention on the Elimination of All Forms of Discrimination Against Women was adopted by the UN General Assembly in 1979 and is often described as the international bill of rights for women. States that are a party to the agreement pledge "to make equality between men and women a reality by providing equal opportunities in all fields, whether political, civil, economic, social or cultural, as well as in family life. Those States also committed themselves to reporting to the Committee on the Elimination of Discrimination Against Women on steps taken to fulfill their obligations." (Source: The UN handbook on the convention and its optional protocol)  States also have the option to sign onto an optional protocol to the convention which allows women whose rights have been violated and who have exhausted national remedies to seek redress from an independent international body. 

The United States has signed this treaty but not ratified it. To be honest, our country does this pretty often. For a treaty to be ratified by the United States, the Senate must advise and consent the President on the treaty by a two-thirds vote. Only after the Senate approves can the President ratify it. Here's what Wikipedia says about this: "While the House of Representatives does not vote on it at all, the requirement for the Senate's advice and consent to ratification makes it considerably more difficult to rally enough political support for international treaties. Also, if implementation of the treaty requires the expenditure of funds, the House of Representatives may be able to block or at least impede such implementation by refusing to vote for the appropriation of the necessary funds."

So what power does an unratified signature have?  "Where the signature is subject to ratification, acceptance or approval, the signature does not establish the consent to be bound. However, it is a means of authentication and expresses the willingness of the signatory state to continue the treaty-making process. The signature qualifies the signatory state to proceed to ratification, acceptance or approval. It also creates an obligation to refrain, in good faith, from acts that would defeat the object and the purpose of the treaty." [Arts.10 and 18, Vienna Convention on the Law of Treaties 1969]

Here's the part that is most relevant to marriage and marital surname decisions:

Article 16

1. States Parties shall take all appropriate measures to eliminate discrimination against women in all matters relating to marriage and family relations and in particular shall ensure, on a basis of equality of men and women:

(a) The same right to enter into marriage;

(b) The same right freely to choose a spouse and to enter into marriage only with their free and full consent;

(c) The same rights and responsibilities during marriage and at its dissolution;

(d) The same rights and responsibilities as parents, irrespective of their marital status, in matters relating to their children; in all cases the interests of the children shall be paramount;

(e) The same rights to decide freely and responsibly on the number and spacing of their children and to have access to the information, education and means to enable them to exercise these rights;

(f) The same rights and responsibilities with regard to guardianship, wardship, trusteeship and adoption of children, or similar institutions where these concepts exist in national legislation; in all cases the interests of the children shall be paramount;

(g) The same personal rights as husband and wife, including the right to choose a family name, a profession and an occupation;

(h) The same rights for both spouses in respect of the ownership, acquisition, management, administration, enjoyment and disposition of property, whether free of charge or for a valuable consideration.

2. The betrothal and the marriage of a child shall have no legal effect, and all necessary action, including legislation, shall be taken to specify a minimum age for marriage and to make the registration of marriages in an official registry compulsory.