An open adoption is one in which a birth mother and prospective adoptive parents know the first and last name of each other. Openness may just be for the duration of an adoption, a few months after placement or may continue on years after a placement.
Contracts or negotiations to keep an open adoption is not legally binding nor is it legally prohibited. Adoptive parents have the final say in who their adopted child may come in contact with. Granted, if the adoptive and birth parents have an agreement to maintain contact, only about a third of the states in the U.S. rule that these agreements are valid if in the child's best interest. These negotiations, if formalized, can be challenged. These agreements may specify the kind of contact that will be made and at what frequency the birth parents can contact the adoptee.
All negotiations must be approved prior to an adoption finalization. Agreements can be changed or voided later post-adoption if the courts are petitioned to do so.
About eight states do not enforce adoption agreements and about 22 states allow contracts to be enforced. Nebraska and Connecticut only allow post-placement contact for children adopted from foster care. Indiana allows contact if a child was adopted over the age of 2 and does not allow enforceable visitation agreements to made for infants.
Other states have different laws regulating the kind of birth relatives considered to be eligible for contact. States such as California allow members of a Native American adoptee's tribe to be considered birth family. Siblings are also considered eligible for visitation or participation in certain states.