Is it permissible to contact the police in a non-Islamic country to report hashish dealers? Does the ruling differ if some of those involved are Muslims? What if the reporting takes place in an Islamic country? Is it true that the impermissibility of working for the police in non-Muslim countries means that it is not permissible to contact them in such cases?

Promoting hashish is an evil in both Islamic law and reason. Therefore, it is lawful to report it, just as other criminals are reported. If the hashish promoter is a Muslim, he is a corruptor on earth, and he is the one who enabled disbelievers to judge him by laws other than Islamic Sharia (definition). Reporting him is considered a form of resisting evil and corruption.