camera script, allow free movement of the camera up to a certain distance.

Seems to me like this is a simple problem. In the Update() just take the distance between the camera and the player, and if it's higher than a certain number, block the movement of the camera. Something like this...

 void Update() {
    bool canMove = true; // Default to letting them move
    float limit = 100; // Play with this setting
 
    // Get an approximate distance from camera and player
    float delta = Mathf.Abs(camera.x - player.x) + Mathf.Abs(camera.z - player.z);
    canMove = (delta<limit);  // the camera is close enough, then we can move it.
 
    // Camera moving code
    if (canMove) {
    // Insert you existing code for moving the camera here.
 
    } //EndIf