Unfortunately, user sessions don't normally remain active after closing the browser.
The temporary cookie used to identify a WebSEAL session is erased when the browser is closed.
However, some browsers (not sure which one exactly) do allow a session to be restored after closing, but this feature is not standard and doesn't exist for all browsers. This requirement would require customization of the browser instead of ISAM (WebSEAL)
Session cookies are removed when a browser is closed. So, in order to keep a session open, the browser would need to be modified instead.