EllisLab/CodeIgniter — comment on commit 5d27c43d29fc049497010ea62ac7877a64bfed92
File: system/core/Security.php line 142
By philsturgeon:

It's nothing to do with loading, its to do with reference access. How do you get to $this in a library without referencing get_instance()?

This does not need to use a class, it's a globally available server variable...