Which amendment prohibits Congress from passing ex post facto laws?

The prohibition of ex post facto laws is specifically articulated in Article I, Section 9 of the Constitution. This clause explicitly restricts Congress from enacting laws that would impose penalties retroactively. An ex post facto law would penalize a person for an action that was not illegal at the time it was committed, undermining the principle of fairness and justice that the legal system upholds.

Understanding the implications of this prohibition is crucial, as it protects individuals from arbitrary legislation that could retroactively affect their rights or criminalize past actions that were legal when they occurred. The founding framers recognized the danger of such laws and aimed to ensure a stable and predictable legal environment.

While the Bill of Rights comprises the first ten amendments to the Constitution and includes important protections for individual liberties, it does not specifically mention the prohibition of ex post facto laws. Similarly, the First and Fifth Amendments deal with freedoms such as speech and due process, but do not address this particular issue directly. This context highlights why the correct answer is centered on the specific constitutional provision.