A Unity component that prevents a user from editing a prefab in the Scene view.

PrefabLock.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

#if UNITY_EDITOR
using UnityEditor;
using UnityEditor.SceneManagement;
#endif

[ExecuteInEditMode]
public class PrefabLock : MonoBehaviour
{
    #if UNITY_EDITOR
    // Update is called once per frame
    void Update()
    {
        if (Application.isPlaying)
        {
            return;
        }

        if (!PrefabUtility.IsPartOfAnyPrefab(gameObject))
        {
            Debug.LogWarning("Must Be On Prefab!");
            this.enabled = false;
            return;
        }

        List<ObjectOverride> overrides = PrefabUtility.GetObjectOverrides(gameObject);

        foreach (ObjectOverride objectOverride in overrides)
        {
            if (objectOverride.instanceObject == this)
            {
                continue;
            }
            
            objectOverride.Revert(InteractionMode.AutomatedAction);
        }

        List<RemovedComponent> removedComponents = PrefabUtility.GetRemovedComponents(gameObject);

        foreach (RemovedComponent component in removedComponents)
        {
            component.Revert(InteractionMode.AutomatedAction);
        }
    }
    
    #endif
}