Which specific clause of the U.S. Constitution most directly restricts federal power regarding immigration enforcement within state borders?

The Tenth Amendment to the U.S. Constitution most directly restricts federal power regarding immigration enforcement within state borders. The Tenth Amendment states that any powers that the Constitution does not specifically give to the federal government, nor deny to the states, are reserved to those respective states, or the people. While the federal government has broad authority over immigration matters due to the Supremacy Clause and the Necessary and Proper Clause, the Tenth Amendment prevents the federal government from commandeering state resources or compelling state officials to enforce federal immigration laws. For example, the federal government cannot legally force state police officers to act as immigration agents if the state's laws do not authorize them to do so. This limitation ensures that states retain some autonomy and are not forced to directly implement federal policies against their will.