HideFlags.NotEditable

Description

The object will not be editable in the inspector.

using UnityEngine;

public class Example : MonoBehaviour
{
    // Create a plane and dont let it be modificable in the Inspector
    // nor in the Sceneview.

    void Start()
    {
        GameObject createdGO = GameObject.CreatePrimitive(PrimitiveType.Plane);
        createdGO.hideFlags = HideFlags.NotEditable;
    }
}