Is it permissible to work in a law firm that handles cases and transactions for non-Muslim companies and individuals, and to represent them against Muslims, and is this considered showing allegiance to them? And is it permissible to carry out tasks for establishing branches for their companies?

Advocacy is permissible if its aim is to establish justice, alleviate harm, and restore rights to their owners, even if they are non-Muslims, and it is permissible to receive a fee for it. As for advocating for falsehood and supporting the oppressor, it is forbidden, and what is earned from it is illicit, because it constitutes cooperation in sin and aggression, and involves engaging in disputes for falsehood. Justice is obligatory even with an enemy.

The criterion for the permissibility or impermissibility of the work lies in the nature of the case. Thus, it is not permissible to defend a criminal or to seek licenses for companies involved in forbidden activities.