Is it permissible to attempt to entrap an official who opposes the Sunnah, speaks ill of the Companions, lies, and steals, by writing secret reports against him?

The matter of the thief should be referred to the authorities to reclaim the right from him. There is no objection to using lawful stratagems to expose him, as cunning is permissible to achieve what is right, as Yusuf (peace be upon him) did. Denying the Sunnah is a serious matter that can lead its perpetrator to disbelief, and people must be warned against this deviant path.