Yes, you can provide your own repositories locally and share them amongst the internal development staff.
Maven isn't designed to forbid use of jars, regardless of where they come from, but if you have internally-developed assets that you want Maven to be able to exploit, they can be published to a local shared registry.
If you have a situation where the desktop developers are denied direct access to the Internet (a tactic that rarely works very well), you can stage/cache the publicly-published items like the
j2ee api jars in your site repository as well.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.