Limited Government: We have a bill of rights
Separation of Powers: Supreme court, President, and Congress
Checks and Balances: The president can veto stuff from congress and congress can override the veto with 2/3 vote. Supreme court can declare things unconstitutional.
Judicial Review: Supreme court can declare things unconstitutional.
Federalism: the theory or advocacy of federal principles for dividing powers between member units and common institutions.
I hope that this is the answer that you were looking for and it has helped you.
Congress had decided that once a slave traveled into a free state, they were free and they could never be enslaved again. But in the Dred Scott decision, they changed their mind and people no longer had to honor "once free, always free."
Hope this helps!
