Cross Browser - Is It Possible For Clients To Disable/disregard A 301 Redirect

I have 2 domains that resolve to my web site www.mysite.com and www.mysitecommonmisspelling.com, plus the IP address. I have some code in my Global.asax file that was intended to force all users and crawlers to only use the main domain, like so:

Protected Sub Application_BeginRequest(ByVal sender As Object, ByVal e As System.EventArgs)

'If the domain isn't the correct top level domain for this environment,

'we want to do a 301 redirect to tell the search engines that this is not the right domain to

'index.
Dim Host As String = Me.EnvironmentHost
Dim CurrentHost As String = Request.Url.DnsSafeHost[code]....

I checked and Google has not indexed any pages on www.mysitecommonmisspelling.com, so they are apparently respecting the 301. However, a few days ago we had a customer on our site who got free shipping because the licensing code that is only registered for www.mysite.com failed (in other words, the browser was able to access www.mysitecommonmisspelling.com). In the past, we have had issues with the 3rd party shipping component because users were able to access the site using the IP address.

In any case, we don't want users to be able to access the site without the correct domain so the SSL certificate doesn't complain.

I have searched for a way to disable 301 redirects in IE7, but there doesn't appear to be a way. So, what I am wondering is if there are any browsers that can disable 301, and if so what kind of workarounds can I put in place to ensure all browsers on my site are going to the main domain, www.mysite.com?