Restraint of or responsibility for a person according to law, such as a guardian's authority (conferred by the court) over the person or property (or both) of his ward.
Source: Children Welfare Information Gateway
Legal custody determines which parent will make decisions concerning the child's or children's health, safety, education, and welfare. One parent can make these decisions alone, which is known as sole legal custody, or both parents retain the right to make these decisions, known as joint legal custody. Joint legal custody means both parents should cooperate on decision-making, but that either parent has the power to make decisions alone. Sole legal custody means only one parent can make decisions and obtain information from the child's or children's school and doctor, for example.
Source: Superior Court of California, County of Sacramento