A more thorough explanation:

The rule of lenity is a principle used in criminal law that states when a law is unclear or ambiguous, the court should interpret it in the way that is most favorable to the defendant. This principle is also known as the rule of strict construction.

The rule of lenity is based on two constitutional objectives. The first objective is the separation of powers, which limits the scope of statutory language in penal statutes. This means that the courts cannot establish the boundaries of a crime and its punishment. The second objective is to protect the legislature's constitutional lawmaking prerogative and limit the courts' encroachment on a legislative function.

Suppose a law states that it is illegal to "possess a firearm in a school zone." However, the law does not define what a "school zone" is. In this case, the rule of lenity would require the court to interpret the law in favor of the defendant. The defendant could argue that they did not know they were in a school zone because the law was unclear. The court would then have to decide whether the defendant's interpretation of the law was reasonable.

Another example is if a law states that it is illegal to "knowingly transport drugs across state lines." However, the law does not define what "knowingly" means. In this case, the rule of lenity would require the court to interpret the law in favor of the defendant. The defendant could argue that they did not know they were transporting drugs because the law was unclear. The court would then have to decide whether the defendant's interpretation of the law was reasonable.

These examples illustrate how the rule of lenity protects defendants from being punished for conduct that is not clearly prohibited by law. It ensures that criminal laws are clear and unambiguous, and that defendants are not punished for conduct that they could not reasonably have known was illegal.