The word here is "ἐξουσία", It means access to something, not entitlement.Rev 22:14 - 14 Blessed are those who wash their robes, so that they will have the right to the tree of life, and may enter the city by the gates.
It gives us the opportunity to become Christians and to go to Heaven, but does not entitle us to become Christians or go to Heaven. Otherwise, the nonelect would be saved, too, and that would be Universalism.Christ's death on the cross gave all humans the right to become Christians and go to Heaven.
Access, not entitlement.This is why Christ died for everyone (John 3:16). Christ's death gives us the right to the tree of life.