How to prevent members of a certain group from filling out, submitting or even viewing a form?

Question

Lets say I have a few users in a group called "Restricted" and I don't want them to be able to view or submit forms. Should I add some code in the Form_Loading event that checks what groups the current user is a member of? If so, how would I prevent the form from loading? So far the code I have doesn't seem to work.

SPGroupCollection grpCol = SPContext.Current.Web.CurrentUser.Groups;

            try
            {
                SPGroup group = grpCol["Restricted"];

                // if this doesn't throw an exception, they are not part of that group, so exit
                return;
            }
            catch (Exception ex)
            {
                // if exception is thrown, they don't belong to that group, so continue                                        
            }

Answer 1

The standard way for SharePoint to handle this is to call:

SPUtility.HandleAccessDenied(new UnauthorizedAccessException());