When a Bishop Becomes Schismatic . . .

. . . then the priest has a choice to make: either follow into schism or find a canonical bishop. It is canon law.

Canon 15. The rules laid down with reference to Presbyters and Bishops and Metro­politans are still more applicable to Patriarchs. So that in case any Presbyter or Bishop or Metropolitan dares to secede or apostatize from the communion of his own Patriarch, and fails to mention the latter’s name in accordance with custom duly fixed and ordained, in the divine Mystagogy, but, before a conciliar verdict has been pronounced and has passed judgment against him, creates a schism, the holy Council has decreed that this person shall be held an alien to every priestly function if only he be convicted of having committed this trans­gression of the law. Accordingly, these rules have been sealed and ordained as respecting those persons who under the pretext of charges against their own presidents stand aloof, and create a schism, and disrupt the union of the Church. But as for those persons, on the other hand, who, on account of some heresy condemned by holy Councils, or Fathers, withdrawing themselves from communion with their president, who, that is to say, is preaching the heresy publicly, and teaching it barehead in church, such persons not only are not subject to any canonical penalty on account of their having walled themselves off from any and all communion with the one called a Bishop before any conciliar or synodal verdict has been rendered, but, on the contrary, they shall be deemed worthy to enjoy the honor which befits them among Orthodox Christ­ians. For they have defied, not Bishops, but pseudo-bishops and pseudo-teachers; and they have not sundered the union of the Church with any schism, but, on the contrary, have been sedulous to rescue the Church from schisms and divisions.
(Ap. c. XXXI; c. XVIII of the 4th; cc. XXXI, XXXIV of the 6th; cc. XII, XIII, XIV of the lst-and-2nd; c. V of Antioch; c. VI of Gangra; cc. X, XI, LXII of Carthage.)

Keyword. sed·u·lous – /ˈsejələs/ adjective – (of a person or action) showing dedication and diligence