Final answer:
George Mason and other Anti-Federalists were concerned that federal laws would take precedence over state laws, potentially overriding the protections and liberties the states' constitutions provided, hence their advocacy for a Bill of Rights.
Step-by-step explanation:
According to Anti-Federalist George Mason, state rights would no longer be protected because national laws and the new Constitution would be stronger than state laws. Mason feared that the lack of a declaration of rights in the federal Constitution meant that the state declarations of rights had no security since federal law would be paramount. Furthermore, many Anti-Federalists shared the concern that individual liberties granted by state constitutions might be overridden by a powerful federal government without a Bill of Rights. This led to a demand for the addition of such protections directly into the Constitution to ensure federal laws would not infringe upon the rights previously secured by the states.