Except, a pastor's call and a ruling elders
differ at this pertinent point:
The pastor's call is a
three-way approval (tripartite), the elder's call is bipartite.
In order for a man to fill an office of the ministry in typical Presbyterian order, there is required
1) the approval of the calling entity
2) the acceptance of the called man
3) the consent of Presbytery
Nor can this call be in any way dissolved, but by the minimal agreement of two of the three, according to good order and discipline.
The complexity of this arrangement, together with the lengthy approval process for a minister from the beginning, makes the judicial process for his removal a practical necessity. He is a man who (unlike the elder) makes his living on the gospel. It's a little more impactful in secular terms (to say nothing of prior investments, and the family-members' lives directly affected) to put a man out of his charge (or the ministry altogether), than it is to rescind an elder's call.
The elder is a servant of the congregation, he is and continues to be a member of some particular congregation when he is called. His service is an agreement between a congregation and him. The congregation might see the need (I think it would be extraordinary) to suspend their previous hopes for the elder's service; but they might will to do this
without prejudice to the man as to his moral character and his doctrine.
Judicial discipline is for correction of wrongdoing. If a congregation wills to end a life-tenure relationship with an elder (or a term-tenure before its course is run), but not for elder misconduct, they are saying: "We did the wrong thing; the error is with us." That may be a blow to an elder's pride, but it is not (as the OPC has written its rules) a disorderly act.
Consider this: an elder is free to resign his charge. He may leave a church, and go elsewhere or not; and his reason might be: "I couldn't herd those goats." Now, there's probably a lot of background to sift through, given such a sentiment. I'm not validating the man's deed or words. But note: this is in essence the same sort of bipartite engagement/withdrawal as when the church draws back from the man they raised over themselves. He says: either they are unleadable, or I'm not the man for the job.
If a church may not withdraw it's consent, then by parity of reasoning an elder may not resign. He must continue to the end, despite his distaste for the job or the members, or his feeling of unfitness. Who is he to argue with the whole, which ever after refuses to reconsider their decision?
When a pastor resigns, it again takes the consent of the congregation, and the acknowledgement of Presbytery. Two agreements may be
sufficient to finally end the relationship, but two (presbytery and congregation) could
conceivably agree against the minister; thus extending his service in a charge over which he has expressed unhappiness.
The different relations to a congregation sustained by ministers and elders give rise to different rules by which those relations are both continued or concluded.