King Maegor's laws
King Maegor's laws, or Maegor's laws, forbid holy men in Seven Kingdoms from being able to bear arms. The laws helped to break the Faith's political power.
When the Faith of the Seven and the Faith Militant rose against King Aenys I Targaryen, he was unable to properly deal with the crisis before his death. His successor, King Maegor the Cruel, outlawed armed holy men and took brutal steps to put down the rebelling orders and the houses supporting them, including offering bounties for their heads. Not even the death of the High Septon and his replacement for a more passive one stopped the determination of the Faith Militant.
Abolishing of Maegor's laws
After the War of the Five Kings in 300 AC, the ruling King Tommen Baratheon, under the edict of his mother and Regent Cersei Lannister, overturn Maegor I Targaryen's laws which forbade holy men from being armed, and the order was reborn.
A Feast for Crows
The Queen Regent, Cersei Lannister, officially reinstates both orders of the Faith Militant in an attempt to secure the support of the new High Septon, the High Sparrow, for her son Tommen. Many knights, including Cersei's cousin Lancel Lannister, join the reformed Warrior's Sons in the aftermath.
Instead of taking the swords out of the hands of the faithful, he should have used them for his own ends.—Cersei Lannister, on King Maegor