Question:
Answer:
The short answer is yes. Once a priest, always a priest. The Church teaches that in the sacrament of holy orders, a ministerial priest receives an indelible mark on the soul:
The three sacraments of baptism, confirmation, and holy orders confer, in addition to grace, a sacramental character or “seal” by which the Christian shares in Christ’s priesthood and is made a member of the Church according to different states and functions. This configuration to Christ and to the Church, brought about by the Spirit, is indelible; it remains for ever in the Christian as a positive disposition for grace, a promise and guarantee of divine protection, and as a vocation to divine worship and to the service of the Church. Therefore, these sacraments can never be repeated (CCC 1121).
You can also reference Hebrews 7:17, which reveals that Christ is a priest forever: “Thou art a priest for ever, after the order of Melchizedek.” Since Catholic priests participate in the priesthood of Christ, it follows that they are priests after the order of Melchizedek as well, and thus priests forever. However, given that the sacramental veils of bread and wine will give way to face-to-face communion with Christ in the fulfillment of the Mass in heaven, that is, “the marriage supper of the Lamb” (Rev. 19:9), there will be no need for priests to celebrate the sacraments, for we will come to their fulfillment in the beatific vision (CCC 1028; see 1137–1139).