Is it permissible to work as a management accountant in a police directorate when there is injustice perpetrated by the police and oppressive laws are applied, and is this work considered assisting in falsehood?

Working in the police force may be permissible if undertaken by a strong and trustworthy individual who supports the oppressed, deters the oppressor, and removes evil. He must be careful not to aid the oppressor. As for administrative positions within the police, if they involve direct participation in or aiding something forbidden, or if they lead to committing forbidden acts or neglecting an obligation, then they are impermissible. If such work is permissible, there is no objection to it, though it is permissible to refrain from it due to the prevalence of injustice. Cooperation is of two types: cooperation in righteousness and piety, which is obligatory, and cooperation in sin and aggression, which is forbidden.