HideFlags.NotEditable  

// Create a plane and dont let it be modificable in the Inspector
// nor in the Sceneview.

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

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Start() {
GameObject createdGO = GameObject.CreatePrimitive(PrimitiveType.Plane);
createdGO.hideFlags = HideFlags.NotEditable;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Start():
createdGO as GameObject = GameObject.CreatePrimitive(PrimitiveType.Plane)
createdGO.hideFlags = HideFlags.NotEditable