Löste det hela själv med;
PHP-kod:
SELECT catalog.*
FROM user, catalog, group, group2user, group2catalog
WHERE group2user.user_id = user.id
AND group2user.group_id = group.id
AND group2catalog.group_id = group.id
AND group2catalog.catalog_id = catalog.id
AND user.id = $user_id
GROUP BY catalog.id