Name those authorities. In the Shafi madhab, it is the opinion of Imam Nawwawi, Imam Ibn Hajar and others that building on braves in a public place is haraam and in a private place, it is makruh so what Shabaab have done is fine according to the madhab of Imam Shafi. Don't let your hatred of Salafi's blind you to the fact that t8hey have done good in Somalia