I needed a quick tag to detect if the page the tag resided in was called using a secure URL. Unfortunately, the CGI function was not easily found, so here it is.
<cfif CGI.HTTPS EQ "off">
<cfset NewLink = "https://" & #CGI.HTTP_HOST# & #CGI.PATH_INFO#>
<cfif #CGI.QUERY_STRING# NEQ "">
<cfset NewLink = NewLink & "?" & #CGI.QUERY_STRING#>
CGI.HTTPS returns "off" if the URL is not of a secure server. Once that is checked, you build the new URL using the next few lines. From there, you can output the new link, or redirect to the new URL.