Views page access callback
Views allows you to set the acess within the UI, you can restrict based on roles or permission. 

Usually that should be enought but if you need to set a custom access callback you can use hook_menu_alter but you will also need to make sure your module is called after the views hook_menu_alter, you can change the weight of your module in the database or you can use hook_module_implements_alter to make sure your module is called after the views module for the menu alter hook.