The legislative branch plays a crucial role in the U.S. government's separation of powers. Congress, divided into the House and Senate, has specific powers like regulating commerce, declaring war, and levying taxes. This system ensures no single branch becomes too powerful. The Constitution's framers designed this structure to prevent tyranny and protect individual liberties. Key concepts include enumerated and implied powers, the nondelegation doctrine, and the system of checks and balances that allows each branch to limit the others' authority.