What is the ruling on praying behind an Imam who has tattoos?

The prayer of an imam who has tattoos and his imamate are valid if he is unable to remove them, due to the certain harm that would result from their removal. However, if he is able to remove them without harm, then his prayer is invalid and his imamate is not valid. Tattoos are forbidden in Islamic law, because the one who applies them and the one upon whom they are applied are cursed. The imamate of a fasiq (transgressor) and a disobedient person is valid, because the fundamental principle is that whoever's prayer is valid for himself, his imamate is also valid. And it is from the Sunnah that the most knowledgeable in recitation among the people should lead them in prayer.