Communion is not permitted for a Catholic that married civilly while a Catholic, without approval of the Church, and that is living as though validly married. St. Pope John Paul II wrote in* Familiaris Consortio*:
Catholics in Civil Marriages
The aim of pastoral action will be to make these people understand the need for consistency between their choice of life and the faith that they profess, and to try to do everything possible to induce them to regularize their situation in the light of Christian principle. While treating them with great charity and bringing them into the life of the respective communities, the pastors of the Church will regrettably not be able to admit them to the sacraments.
Divorced and Remarried Catholics
However, the Church reaffirms her practice, which is based upon Sacred Scripture, of not admitting to Eucharistic Communion divorced persons who have remarried. They are unable to be admitted thereto from the fact that their state and condition of life objectively contradict that union of love between Christ and the Church which is signified and effected by the Eucharist. Besides this, there is another special pastoral reason: if these people were admitted to the Eucharist, the faithful would be led into error and confusion regarding the Church’s teaching about the indissolubility of marriage.
Reconciliation in the sacrament of Penance which would open the way to the Eucharist, can only be granted to those who, repenting of having broken the sign of the Covenant and of fidelity to Christ, are sincerely ready to undertake a way of life that is no longer in contradiction to the indissolubility of marriage. This means, in practice, that when, for serious reasons, such as for example the children’s upbringing, a man and a woman cannot satisfy the obligation to separate, they “take on themselves the duty to live in complete continence, that is, by abstinence from the acts proper to married couples.”(180)
vatican.va/holy_father/john_paul_ii/apost_exhortations/documents/hf_jp-ii_exh_19811122_familiaris-consortio_en.html