Third Council of Constantinople (680-681)
This council issued a number of canons now widely ignored (and rightly so). Continuing the limitation on theological debate of the Fifth Council, canon 19 forbids any "new" interpretation of Scripture. Canon 31 forbids liturgies in private houses (i.e. house churches). Canon 27 forbids clergy to wear secular clothes. Canon 33 denies recognition to baptisms performed by the Armenian church. Canon 51 prohibits public theatres and theatrical performances.
(one can easily see why this council presents difficulties in the modern world. It is not recognized as binding by any of the Churches of the Three Councils (like OCCA).