The Songhai empire expanded its wealth and power by:

Songhai rulers subsequently took advantage of the weakened Mali Empire to expand Songhai rule. Under the rule of Sonni Ali, the Songhai surpassed the Malian Empire in area, wealth, and power, absorbing vast areas of the Mali Empire and reached its greatest extent.

( i'm learning about the same thing )

If he breaks the law then he had to resign from his post and so he'll lose his/her powers.