Give user access by category name

I’ve set a number of groups in relation to category names,

Now I’m trying to give user access page content by getting the category name and matching it to the user group?

<?php
$user_id = get_current_user_id();
$groupname = get_single_cat_title();
$group = Groups_Group::read_by_name( $groupname );
if ( Groups_User_Group::read( $user_id, $group->group_id ) ) { 

echo 'access granted';

} else {

echo 'access denied';

}
?>

http://wordpress.org/plugins/groups/