How Excommunication Works

Question: How does excommunication work?

Based on the words of Christ Who said what is bound on earth is bound in heaven and what is loosed on earth is loosed in heaven in regards to the "keys" of the Church:

If you are validly excommunicated (note that sometimes an excommunication is invalid, e.g., St. Joan of Arc) and you do not have the censure lifted or at least form the intent to reform or muster the requisite contrition for the delict, and die while in the state of excommunication, then, you do, in fact, show up to the particular judgment, excommunicated. In this sense, the Church does have jurisdiction, at least as far as Christ will uphold the adjudication.

I was recently told by an expert in canon law that the Church does not have jurisdiction in the next life. He said this in reference to my assertion that an excommunication would necessarily follower the sinner in the next life if not rectified.

Answer: 
The theologian is obviously Lutheran, because the idea that the Church does not have jurisdiction in the next life constituted the central error in Martin Luther's 95 Theses.

That having been said, excommunication is a juridical ruling about participation in the temporal life of the Church (i.e., the individual is barred from participation in most sacraments). Now, certainly, this lack of access to sacramental grace may also redound to eternal life, but God also might, in his infinite knowledge and mercy, take into account aspects of the situation which the Church, in her finite knowledge, is unable to consider.

Thus, excommunication is not a guarantee that the person excommunicated is absolutely cut off from heaven. Excommunication is objectively something to be avoided, but subjectively we cannot be sure the excommunicated person is in hell - only God and the individual who has died has absolute surety of how that person's eternal existence will be spent.

Excommunication means that, from an external viewpoint, the Church judges that the individual has distanced himself from God so effectively that he may well be damning himself to hell.

But the Church's judgement is not a judgement of the actual state of the individual's soul. It is merely a judgement about all that the Church knows about the person's public disposition. It is a judgement about the external, public factors. There may well be internal aspects of which the Church knows nothing, and the Church's judgement does not presume to include those aspects.

Further Question:
But what if the application of the penalty was subjectively in play, that is, total and utter culpability? What do we make of the Lord's words that what is bound on earth is bound in heaven? If the Lord discounts the censure in the next life, then would we not deduce that the Church's power to excommunicate expires at the death of the subject who labors under the penalty?

Deeper Answer:
Not at all.

The Church absolutely has power over the next life. That's what the doctrine of indulgences is all about. It's just that She chooses not to exercise it to condemn anyone to hell, for even God Himself does not condemn sinners, rather, the sinners condemn themselves.

Christ came into the world to save it, not to condemn it. The Church, as the Bride of Christ, imitates Her Spouse by using Her power (which comes from Christ) to do Christ's work - to save the world, not to condemn it.

Christ is Judge, but has not yet returned as Judge, so it is not the Church's role to negatively judge anyone's soul. Yet.