Slahi 's cousin and former brother-in-law is Mahfouz Ould al-Walid , also known as Abu Hafs al-Mauritania . Before the September 11 attacks in the United States , Al-Walid was a spiritual adviser to Osama bin Laden , was on the shura council of al Qaeda , and headed the sharia council . However , two months before the attacks , al-Walid , along with several other al Qaeda members , wrote a letter to bin Laden opposing the planned attacks . Al-Walid left al Qaeda after the attacks
September 11 attacks
September 11 attacks
Mohamedou Ould Slahi