Final answer:
The constitutional basis for the nationalization of the Bill of Rights is the Fourteenth Amendment, which requires states to uphold provisions of the Bill of Rights.
Step-by-step explanation:
The constitutional basis for the nationalization of the Bill of Rights is the Fourteenth Amendment.
Beginning in 1897, the Supreme Court found that various provisions of the Bill of Rights must be upheld by the states, even if their state constitutions and laws do not protect them as fully as the Bill of Rights does. This process is known as selective incorporation and effectively inserts parts of the Bill of Rights into state laws and constitutions.
When cases arise to clarify specific issues and procedures, the Supreme Court decides whether state laws violate the Bill of Rights and are therefore unconstitutional.