If one's churh does not believe in the real presence then there is no communion.
An Orthodox Christian may receive Holy Communion in a Catholic church under specific, exceptional circumstances. According to Canon 844 §3 of the 1983 Code of Canon Law, Catholic ministers may licitly administer the sacraments of Eucharist, Penance, and Anointing of the Sick to members of Eastern Churches not in full communion with the Catholic Church—such as the Orthodox—provided they seek the sacraments of their own accord and are properly disposed. This provision reflects the Catholic Church’s recognition of the valid sacraments and apostolic succession within the Orthodox tradition. However, it is not a general permission; it applies only when there is necessity or genuine spiritual benefit, and the Orthodox communicant must freely request the sacrament without coercion or disregard for their own ecclesial discipline.
Nonetheless, the Orthodox Church generally prohibits its faithful from receiving Communion outside its own canonical boundaries. As articulated by the Orthodox Church in America, Eucharistic sharing is seen not merely as a gesture of hospitality but as a visible sign of full ecclesial unity. Thus, even if a Catholic priest is willing to offer Communion, an Orthodox Christian is ordinarily bound by their own Church’s discipline not to receive it. The Catholic Church respects this restriction and does not encourage Orthodox Christians to contravene their own ecclesial norms. In practice, therefore, while Catholic law permits such reception under defined conditions, Orthodox discipline typically renders it impermissible. This tension underscores the theological significance of Eucharistic communion as both a sign and fruit of full ecclesial unity.
