404 Page Not Working

On my site, http://www.dumblaws.com, I have set up a custom 404 page in my theme (404.php). However, if you go to a completely gibberish URL inside the site, you are shown an archive page (“Dumb Laws in”) instead of a 404. The archive page has no category (a state or country, in this case) so it displays an arbitrary set of laws.

Any idea what I can do to get the site to show a 404 when it should?

Thanks!