WordPress at a glance
function is not described

users_can_register_signup_filter() WP 3.0.0

Check whether users can self-register, based on Network settings.

No Hooks.

Return

true/false.

Usage

users_can_register_signup_filter();

Code of users can register signup filter: wp-includes/ms-functions.php VER 5.1.1

<?php
function users_can_register_signup_filter() {
	$registration = get_site_option( 'registration' );
	return ( $registration == 'all' || $registration == 'user' );
}