Camera rotating past clamp

why is the camera free to rotate any way it wants?

 using UnityEngine;
 using System.Collections;
 
 public class CameraController : MonoBehaviour {
     
     public int Sensitivity;
     
     private float MouseY;
     private float MouseYSet;
     private float CameraAngle;
     public float MaxAngle;
 
     public GameObject CameraTarget;
     
     void Start () {
         
     }
     
     void Update () {
         // Rotation controls
         MouseY -= Input.GetAxisRaw ("Mouse Y");
         MouseY = Mathf.Clamp (MouseY, -MaxAngle, MaxAngle);
         if (MouseYSet != MouseY)
         {
             transform.Rotate ((MouseY - MouseYSet) * Sensitivity * 10, 0, 0);
             MouseYSet = MouseY;
         }
     }
 }