Reference: Fataawa al-‘Aqeedah – Question 373, Page 384
Question: What is the ruling regarding praying against the ruler who does not rule according to what Allaah has revealed?
Response: You [should] pray for his guidance and success, and that Allaah facilitates the rectification [of the affairs] of his people (citizens) at his hands, and thereby rules them with the Sharee’ah of Allaah.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet Muhammad ﷺ and his family and his companions.