It's that pesky10th Amendment (ratified in 1791) :
“The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.”
According to James Madison (a federalist) the Constitution maintains the sovereignty of states by enumerating very few express powers to the federal government, while “those which are to remain in the State governments are numerous and indefinite.”
It's that pesky10th Amendment (ratified in 1791) :
“The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.”
According to James Madison (a federalist) the Constitution maintains the sovereignty of states by enumerating very few express powers to the federal government, while “those which are to remain in the State governments are numerous and indefinite.”
It doesn't get much clearer than that.