This is the equal protection clause of the 14th amendment.
"No state shall make or enforce any law which shall abridge the priviledges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws."
It seems to me that the Supreme Court has to decide whether the fetus has an overriding right to life or not. If it does, then it has to protect that right from coast to coast. If the fetus doesn't have that right, then the mother has rights that have to be protected. What would be a logical absurdity would be to say that a fetus has a right to life in Texas but not in California.