Please answer a question about the following article about Nigeria:

The vast majority of Muslims in Nigeria are Sunni belonging to Maliki school of jurisprudence; however, a sizeable minority also belongs to Shafi madhhab. A large number of Sunni Muslims are members of Sufi brotherhoods. Most Sufis follow the Qadiriyya, Tijaniyyah and/or the Mouride movements. A significant Shia minority exists (see Shia in Nigeria). Some northern states have incorporated Sharia law into their previously secular legal systems, which has brought about some controversy. Kano State has sought to incorporate Sharia law into its constitution. The majority of Quranists follow the Kalo Kato or Quraniyyun movement. There are also Ahmadiyya and Mahdiyya minorities.

What Islamic law is being used in some Nigerian states?
Sharia