Should Catholics ignore Hebrews 13:3 if a Prisoner was excommunicated?
Remember them that are in bands, as if you were bound with them; and them that labour, as being yourselves also in the body. - Hebrews 13:3
Douay-Rheims
The short answer is no.
Does excommunication block Prisoners from prison ministry?
Again the short answer no, unless one is talking about serving at a Catholic mass or reading at Catholic mass in which case the answer is yes.
If a prisoner has been excommunicated, Then Catholics should feel the need to observe Hebrews 13:3!
Having volunteered in prison ministry, both in my own country (Canada) and in super max facilities in the USA, I can affirm to you that no Catholic is blocked from any form of prison ministry whatsoever.
Under current Catholic canon law, excommunicates remain bound by ecclesiastical obligations such as attending Mass, even though they are barred from receiving the Eucharist and from taking an active part in the liturgy (reading, bringing the offerings, etc.). "Excommunicates lose rights, such as the right to the sacraments, but they are still bound to the obligations of the law; their rights are restored when they are reconciled through the remission of the penalty." They are urged to retain a relationship with the Church, as the goal is to encourage them to repent and return to active participation in its life.
In Latin Catholic canon law, excommunication is a rarely applied censure and thus a "medicinal penalty" intended to invite the person to change behaviour or attitude, repent, and return to full communion. It is not an "expiatory penalty" designed to make satisfaction for the wrong done, much less a "vindictive penalty" designed solely to punish: "excommunication, which is the gravest penalty of all and the most frequent, is always medicinal", and is "not at all vindictive".
Excommunication in the Latin Church is governed by the 1983 Code of Canon Law (CIC). The 1983 Code specifies various sins which carry the penalty of automatic excommunication: apostasy, heresy, schism (CIC 1364:1), violating the sacred species (CIC 1367), physically attacking the pope (CIC 1370:1), sacramentally absolving an accomplice in a sexual sin (CIC 1378:1), consecrating a bishop without authorization (CIC 1382), directly violating the seal of confession (1388:1), and someone who actually procures an abortion.
Under current Catholic canon law, excommunicates remain bound by ecclesiastical obligations such as attending Mass, even though they are barred from receiving the Eucharist and from taking an active part in the liturgy (reading, bringing the offerings, etc.). "Excommunicates lose rights, such as the right to the sacraments, but they are still bound to the obligations of the law; their rights are restored when they are reconciled through the remission of the penalty." They are urged to retain a relationship with the Church, as the goal is to encourage them to repent and return to active participation in its life.
In the Catholic Church, excommunication is normally resolved by a declaration of repentance, profession of the Creed (if the offense involved heresy) and an Act of Faith, or renewal of obedience (if that was a relevant part of the offending act, i.e., an act of schism) by the excommunicated person and the lifting of the censure (absolution) by a priest or bishop empowered to do this. "The absolution can be in the internal (private) forum only, or also in the external (public) forum, depending on whether scandal would be given if a person were privately absolved and yet publicly considered unrepentant."[37] Since excommunication excludes from reception of the sacraments, absolution from excommunication is required before absolution can be given from the sin that led to the censure. In many cases, the whole process takes place on a single occasion in the privacy of the confessional. For some more serious wrongdoings, absolution from excommunication is reserved to a bishop, another ordinary, or even the Pope. These can delegate a priest to act on their behalf. - Excommunication (Catholic Church)
The Church remains a mother at heart and desires her children to return to the sacramental practice of their faith, whether in prison or not.
Those confined to a penal institution, still retain the possibility of going to mass, but are not allowed to receive the sacraments until they first receive sacramental forgiveness from the Church first.
Thus prisoners are quite free to ask Catholic pastors council on matter of internal forum, the sacrament of penance and advice on spiritual matters.
Prisoners, in general, have the right to access the prison chaplain, whether Catholic or not, for religious literature and reading material. The security level of a particular offender may make these situations much more complicated. The prisoner on death row has a greater difficulty in getting access to a priest than an inmate in a minimum prison institution, but that is a matter outside the hands of the Church.