Finally, Jesus says, "Whatever you declare bound on earth shall be bound in heaven; whatever you declare loosed on earth shall be loosed in heaven." This is rabbinic terminology. A rabbi could bind, declaring an act forbidden or excommunicating a person for serious sin; or a rabbi could loose, declaring an act permissible or reconciling an excommunicated sinner to the community.
But on the point to which you did respond, I think you've misunderstood exactly what the sacraments and excommunication from them means.
The sacraments are the ordinary means of grace - the way that Christ ordained for his Church to share the merits of His blood with believers.
If a person does something to incur excommunication, then they have denied themselves the sacraments: the ordinary means of grace.
But there are also extraordinary means of grace - one salient Scriptural example is Christ's appearance to Saul on the road to Damascus: a special grace of salvation being shared with an unbeliever who was actively persecuting the Church.
Excommunication does not mean the automatic and irreversible death of the soul: it is a warning to someone who is in peril.
The final arbiter of a soul's destiny, as He is of everything else, is God. The Church is God's vicegerent and servant.