<?php
/*
This snippet will force event pages to use SSL
http://wp-events-plugin.com/tutorials/how-to-safely-add-php-code-to-wordpress/
 */
function my_em_force_ssl( $template ){
    if( !is_ssl() && em_is_event_page() ){
        wp_redirect(str_replace('http:','https:', get_permalink()));
        die();
    }
    return $template;
}
add_filter('template_redirect', 'my_em_force_ssl', 10 );