How should Muslim rulers who do not rule by Sharia in Muslim lands be dealt with?

The Noble Messenger (peace be upon him) clarified the methodology that should be followed with rulers who contravene Islamic law, saying: "There will be rulers, and you will recognize some of their actions and disapprove of others. So, whoever recognizes [the wrong] is absolved, and whoever disapproves is safe, but whoever is pleased and follows..." He was asked: "Should we not fight them?" He replied: "No, not as long as they pray." Narrated by Imam Muslim.

Al-Nawawi's explanation of the Hadith: - "So whoever dislikes it is absolved": Whoever dislikes the reprehensible act in their heart is absolved from its sin and punishment. This applies to those who cannot denounce it with their hand or tongue. - "Whoever recognizes it is absolved": Whoever recognizes the reprehensible act and it is not ambiguous to them, their path to absolution is by changing it with their hand or tongue. If unable, then they should dislike it in their heart. - "But whoever is pleased and follows": The sin and punishment fall upon whoever is pleased with the reprehensible act and follows it. - "No, as long as they pray": It is not permissible to rebel against rulers merely for injustice or immorality, as long as they do not alter any of the fundamental principles of Islam.