Is it permissible for someone elected by employees as a union representative to accept an administrative promotion from the company's management during their term of union office?

If the promotion violates the regulations of the syndicate which the elected member has accepted, then he must not accept it. This is based on the general saying of the Prophet, peace be upon him: "Muslims are bound by their conditions," and due to the concern that it might be a bribe to the syndicate member to favor the company's management and overlook the rights of the workers.