Final answer:
Article I Section 9 of the US Constitution prohibits Congress from exercising certain powers, such as banning the importation of slaves, denying the right to a trial by jury, and granting titles of nobility.
Step-by-step explanation:
Article I Section 9 of the US Constitution prohibits Congress from exercising certain powers. These include banning the importation of slaves before 1808 (which became unenforceable after the 13th Amendment abolished slavery), denying the right to a trial by jury, granting titles of nobility, taxing exports or imports between states, passing laws that favor one state over another, and exercising powers reserved for the states.
Additionally, Congress is forbidden from passing laws that threaten the federal system established by Congress. It cannot suspend the writ of habeas corpus, pass bills of attainder, or enact ex post facto laws, all of which protect personal liberties. Congress is also required to provide a regular accounting of government expenditures and is prohibited from granting titles of nobility without congressional approval.