Lock and unlock the current GameObject selection.

LockSelection.cs

using UnityEngine;
using UnityEditor;

static class LockObjects
{
	[MenuItem("Edit/Lock Selection &l")]
	static void LockSelected()
	{
		foreach (var o in Selection.gameObjects)
			o.hideFlags = o.hideFlags | HideFlags.NotEditable;
	}

	[MenuItem("Edit/Unlock Selection &#l")]
	static void UnlockSelected()
	{
		foreach (var o in Selection.gameObjects)
			o.hideFlags = o.hideFlags & (~HideFlags.NotEditable);
	}
}