Sample for StateMachineBehaviour

ForbidWalk.cs

using UnityEngine;
using System.Collections;

public class ForbidWalk : StateMachineBehaviour {

	 // OnStateEnter is called when a transition starts and the state machine starts to evaluate this state
	override public void OnStateEnter(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) {
        animator.SetBool("CanWalk", false);
	}

	// OnStateUpdate is called on each Update frame between OnStateEnter and OnStateExit callbacks
	//override public void OnStateUpdate(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) {
	//
	//}

	// OnStateExit is called when a transition ends and the state machine finishes evaluating this state
	override public void OnStateExit(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) {
        animator.SetBool("CanWalk", true);
	}

	// OnStateMove is called right after Animator.OnAnimatorMove(). Code that processes and affects root motion should be implemented here
	//override public void OnStateMove(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) {
	//
	//}

	// OnStateIK is called right after Animator.OnAnimatorIK(). Code that sets up animation IK (inverse kinematics) should be implemented here.
	//override public void OnStateIK(Animator animator, AnimatorStateInfo stateInfo, int layerIndex) {
	//
	//}
}

Player.cs

using System.Collections;
using UnityEngine;

[RequireComponent(typeof(Animator))]
public class Player : MonoBehaviour {
  
    void Update () {
      var animator = GetComponent<Animator>();

	    if(animator.GetBool("CanWalk"))
      {
      }
    }
}