Final answer:
The principle of limited government limits Congress' powers, including the prohibition of bills of attainder, ex post facto laws, and suspending the writ of habeas corpus. The Bill of Rights also safeguards individual liberties against national government encroachment.
Step-by-step explanation:
The constitutional principle that also limits Congress' powers is the principle of limited government, which is embedded within the Constitution to ensure the protection of citizens' liberties against legislative overreach. Legislation passed by Congress is subject to various restrictions, such as the prohibition against passing bills of attainder, the forbidding of ex post facto laws, and the limitation on the ability to suspend the writ of habeas corpus. Moreover, the Constitution imposes additional layers of scrutiny on Congressional power through elements like the Necessary and Proper Clause and the Commerce Clause, whose interpretation by the Supreme Court has shaped the balance of federal power. Importantly, the Bill of Rights further safeguards individual liberties by prohibiting the national government from encroaching on fundamental rights like freedom of speech, press, religion, and assembly.