The Constitution assigns responsibility for making laws to the legislative branch, Congress. It provides for a bicameral Congress consisting of the House of Representatives and the Senate, as well as a system for selecting electoral votes and laying down rules for the office of President and Vice President. It also outlines the rules of federal courts.
Article IV lays down a legal framework for state-to-state relations, including regulating interstate commerce, the right to move freely among states, and the privileges and immunities of citizens of other states. This includes a clause that states may not discriminate in many ways, or increase penalties, against citizens of other states when convicting them for crimes.
One of the major purposes of the Constitution is to protect citizens from overreaching by their government. The Framers inserted several provisions that prevent the federal government from doing anything that violates citizens’ rights, such as prohibiting ex post facto laws (laws that punish conduct that was not illegal at the time it was performed) and bills of attainder (which single out individuals for punishment).
Another purpose is to guarantee the rights of the people to vote, and to keep the state governments in check. Article II sets out the electoral process, including a system for electing the president through the Electoral College. It also lays down rules for determining eligibility to be President, such as the requirement that they be natural-born citizens at least 35 years old and that they have been in the United States for at least 10 years.