An interdict is a censure, or prohibition, excluding the faithful from participation in certain holy things, such as the Liturgy, the sacraments (excepting private administrations of those that are of necessity), and ecclesiastical burial, including all funeral services.
Exceptions were made for the dying, and local interdicts were almost entirely suspended on five feasts of the year: Christmas Day, Easter Sunday, Pentecost, Corpus Christi and the Assumption of Mary.
While mere attendance by them did not require that they be expelled, those well-known to be under interdict were to be prevented from taking any active part.
One who is under interdict is also forbidden to take any ministerial part (e.g., as a reader if a layperson or as a deacon or priest if a clergyman) in the celebration of the Eucharist or of any other ceremony of public worship.
However, in the case of a ferendae sententiae interdict, one incurred only when imposed by a legitimate superior or by sentence of an ecclesiastical court,[6] those affected are barred from Holy Communion[7] (see canon 915), and if they violate the prohibition against taking a ministerial part in celebrating the Eucharist or some other ceremony of public worship, they are to be expelled or the sacred rite suspended, unless there is a grave reason to the contrary.
[10] Automatic interdict is also incurred by anyone falsely accusing a priest of soliciting sexual favours in connection with Confession[11] or attempting to marry while having a perpetual vow of chastity.
[12] An interdict is also the censure that canon law says should be imposed on someone who, because of some act of ecclesiastical authority or ministry, publicly incites to hatred against the Holy See or the Ordinary, or who promotes or takes up office in an association that plots against the Church,[13] or who commits the crime of simony.