Query/filter by custom field?

Here is the snippet from my functions.php:

add_action( 'cn_metabox', 'cn_register_merit_badge_metabox' );
 
function cn_register_merit_badge_metabox() {

   $atts = array(
		'title'    => 'Merit Badge Counselor',
		'id'       => 'merit_badge_counselor',
		'context'  => 'normal',
		'priority' => 'core',
		'fields'   => array(
			array(
               'name'        => 'Merit Badges',    // Change this field name to something which applies to you project.
               'show_label'  => TRUE,             	// Whether or not to display the 'name'. Changing it to false will suppress the name.
               'id'          => 'merit_badges', 	// Change this so it is unique to you project. Each field id MUST be unique.
               'type'        => 'checkboxgroup',  	// This is the field type being added.
               'options'     => Merit_Badge::merit_badge_names(),
               'default'     => '',                // This is the default selected option. Leave blank for none.
            ),
		),
	);

	cnMetaboxAPI::add( $atts );
}

I have a static class Merit_Badge, that maintains a list of merit badges for our scout troop. The static method, returns an associative array of merit badge ids and names.

Thanks!