Final answer:
The Second Amendment of the US Constitution does not explicitly address the restriction of guns in schools. However, it establishes the right of citizens to possess firearms for lawful purposes. Interpretation of the Second Amendment has been debated and influenced by court rulings.
Step-by-step explanation:
The part of the US Constitution that allowed Congress to pass a law to restrict guns in schools is not explicitly stated. However, the Second Amendment, which is part of the US Bill of Rights, establishes the right of citizens to possess firearms for lawful purposes. The interpretation of the Second Amendment has been subject to debate and court rulings. In recent years, there has been increased conflict over gun control laws and the Second Amendment due to school shootings and gun violence.