A more thorough explanation:

The Magna Carta was a charter of rights agreed to by King John of England in 1215, and was Europe’s first written constitution. Prior to the implementation of the Magna Carta, English monarchs were considered above the law of the land and ruled with relatively absolute power.

For example, King John had the power to imprison anyone he wanted without a trial or a reason. This meant that people could be locked up for no reason at all, and there was nothing they could do about it.

King John was pressured into agreeing to the Magna Carta to make peace in England, as barons from the north and east of England rebelled against his rule and demanded protection from the king’s unbridled power.

The Magna Carta created a legal system by which the king had to abide, instilling protections for the clergy and nobility. The Magna Carta was the basis for English common law, and thereby indirectly also had influence on American law.

For example, the Magna Carta introduced the concept of a habeas corpus petition. This meant that people who were imprisoned had the right to go to court and ask for a reason why they were being held. This is still a fundamental right in many countries today.

The Founding Fathers of the United States particularly admired the charter’s rebellious nature against the English throne. The writers of the Bill of Rights and state constitutions were inspired by concepts born in the Magna Carta: that a government should be constitutional, that the law of the land should apply to everyone, and that certain rights and liberties were so fundamental that their violation was an abuse of governmental authority.

Although the Magna Carta was primarily meant to protect the powerful Church and wealthy nobility in medieval feudal England, it introduced legal concepts that persisted over time and came to be found in American law.

For example, the Magna Carta guaranteed that people could not be imprisoned, outlawed, exiled, or have their possessions or land confiscated without the lawful judgment of their social equals, paving the way for trial by a jury of one’s peers. This meant that people had the right to a fair trial, and that they could not be punished without a good reason.

Moreover, the Magna Carta established a council of barons as a predecessor to Parliament, which monitored the king’s actions to ensure he abided by the new law and rectified breaches of the law. This council was therefore an early example of a checks and balances safeguard.