(Don Hubin is a professor of philosophy at the Ohio State University specializing in Philosophy of Law and related fields. He is also Director of the Columbus Chapter of PACE.)

The argument presented here is simple, but powerful. Fundamental human rights, recognized by the Constitution, ought not, legally or morally, to be suspended or denied without just cause and due process of law. This is especially important when these rights protect important human interests. Parental rights are fundamental human rights recognized by the Constitution. Furthermore, they protect important human interests of both parents and children. These rights are typically and systematically suspended or denied in divorce proceedings. The state's interference with these rights during divorce proceedings requires strict judicial scrutiny because the procedures involve the direct and substantial deprivation of fundamental rights and impose an undue burden on one parent (and,I believe, often on the children). Our current procedures for determining custody of children during the pendency of a divorce case fail the strict scrutiny they demandthey deprive individuals of fundamental, constitutionally recognized, human rights without just cause or due process of law.
Fidelity to the Constitution and to the human rights it seeks to protect requires that we modify our practices. It requires a presumption in favor not only of joint legal custody, but of a fairly equal division of the children's time between the parents. Obviously, one of the most important of the parental rights is the right to companionship with one's children. Both parents have equal rights to this, and it should be the presumption of the court that this benefit and responsibility will be equally shared. Furthermore, the effective exercise of many of the other parental rights involves having reasonable physical custody of the children.
"Lagging Behind the Times: Parenthood, Custody, and Gender Bias in the Family Court" by Cynthia A. McNeely, Florida State University Law Review, 25(1998):891-956.
"Parental Rights and Due Process" by Donald C. Hubin, Journal of Law and Family Studies, 1(1999):123-150.
The U.S. Supreme Court has considered the issue of parental rights on numerous occasions. Since the early 1920s, the Court has issued a series of decisions holding that parenting is a fundamental Constitutional right. Rick Thoma´s Lifting the Veil site, gives summaries of major Supreme Court decisions addressing parental rights, and links to a full-text copy of the decision.
A number of law review articles have explored the implications of the Supreme Court's classification of parental rights as fundamental to the issue of how the states determine custody of minor children upon divorce of their parents.

"Joint Custody: Constitutional Imperatives" by Holly L. Robinson, Cincinnati Law Review, 54(1985):27-65.
"Joint Custody as a Fundamental Right" by Ellen Canacakos, Arizona Law Review, 23(1981):785-800.