if (!CRM_Core_Permission::check('view contacts')) { CRM_Utils_System::permissionDenied(); }This code checks if the current user has permission to view contacts before allowing them to access the contact page. If the user does not have permission, the CRM_Utils_System::permissionDenied() function will be called, displaying an error message to the user. Package library: This function is part of the core CiviCRM PHP library and can be found in the file CRM/Utils/System.php.