Can I redirect the user to a custom page if the deletion is not allowed

Method 1: Using the `return` Parameter

The `com_user` component accepts a `return` parameter to specify where to redirect the user after login. You can use this parameter to redirect the user to a custom page.

For example, you can use the following code to redirect the user to a custom page:

php
$uri = JFactory::getURI();
$uri->setVar('return', 'index.php?option=com_mycomponent&view=myview');

Method 2: Creating a Plugin

You can create a plugin to handle the redirection. Here is an example of how you can use the `onUserBeforeDelete` event in a Joomla plugin to redirect unauthorized users to a custom page:

php
class PlgUserExample extends JPlugin
{
    public function onUserBeforeDelete($user)
    {
        // Check if the user is unauthorized
        if (!$user->authorized) {
            // Redirect to a custom page
            $url = JRoute::_('index.php?option=com_mycomponent&view=myview', false);
            $app = JFactory::getApplication();
            $app->redirect($url);
        }
    }
}

Method 3: Using a Placement Menu Reference

Another approach is to create a placement menu reference. This is a menu group that is not attached to a module and is displayed on the website. You can use this reference to redirect unauthorized users to a custom page.

1. Create a new menu item of type "Menu Alias" and point it to the placement menu reference.
2. Set the access level of the placement menu reference to "Registered" or any other level you want to restrict.
3. When an unauthorized user tries to access the restricted content, they will be redirected to the login page. After logging in, they will be redirected to the custom page specified in the placement menu reference.

These methods allow you to redirect unauthorized users to a custom page instead of the default Joomla login page.