What reason most closely illustrates why the national government was unable to maintain law and order under the Articles of Confederation?

The Articles of Confederation were aproved by Congress in 1777 and ratified in 1781. The government was inefficient under them, the relations between the states were chaotic. There was no real executive power, neither a judicial branch. The Articles' Rule of unanimity was a disaster. During the Shay's Rebellion, in 1786, the national government was unable to act, because the Articles deprived the government of many essential powers.