Family law is the branch of law dealing with family relations, including divorce, adoption, paternity, custody, and support. Most family law issues, including marriage in particular, are regulated by the states.

State regulation of family law issues are limited by the federal Constitution. The Tenth Amendment requires that powers not granted to the national government nor prohibited to the states are reserved to the states.

The rationale for allowing state regulation of family law issues is that there is no grant of power to the federal government over family law issues. As applied to family law issues, the Tenth Amendment to the U.S. Constitution prohibits federal courts from issuing divorce, alimony, and child custody decrees.

Each state has developed its own body of family laws. In addition to developing family law, the states are responsible for administering and enforcing their own family law rules. Occasionally these state rules or their enforcement run afoul of various Constitutional restrictions. The federal courts have jurisdiction to decide whether state family laws are Constitutional.

Most states have specialized family law courts that hear marriage, divorce, adoption, paternity, custody, and support cases.