Article I

Article I creates the legislative branch, establishes the bicameral structure of the House and Senate, and, in Section 8, lists Congress’s enumerated powers — taxing, spending, regulating interstate commerce, declaring war, and roughly twenty others, closed out by the Necessary and Proper Clause. Section 9 then lists specific things Congress cannot do, including suspending habeas corpus except in rebellion or invasion, and passing bills of attainder or ex post facto laws.

The framers placed the legislative branch first and gave it the most detailed, specific list of powers of any article, reflecting their view — shaped by experience with an overreaching king — that the branch closest to the people should hold the most clearly constrained and enumerated authority, in contrast to the more open-ended language used for executive power in Article II.

Common misconception: people often assume Article I gives Congress unlimited lawmaking power over anything of national importance. Congress can only legislate within its enumerated (and Necessary-and-Proper-derived) powers; unlike state legislatures, which have broad general police power, Congress must be able to tie any given law back to a specific constitutional grant of authority, at least in theory — a limitation increasingly stretched but never formally erased.