pfSense

If I type from cli:

easyrule block wan Kids_Devices
Tried to block invalid address: Kids_Devices

The eaysrule docs claim:

The source of traffic to block.

Can be an IPv4/IPv6 address, subnet, alias name, or special network name such as any, pppoe or l2tp.

The GUI code seems to only allow IP's and subnets.

function easyrule_parse_block($int, $src) {
    if (!empty($src) && !empty($int)) {
        $src = trim($src, "[]");
        if (!is_ipaddr($src) && !is_subnet($src)) {
            return gettext("Tried to block invalid address:") . ' ' . htmlspecialchars($src);
        }
        $int = easyrule_find_rule_interface($int);
        if ($int === false) {
            return gettext("Invalid interface for block rule.");
        }
        switch ((string)easyrule_block_host_add($src, $int)) {
            case "exists":
                return gettext("Block entry already exists.");
                break;
            case "invalid":
                return gettext("Invalid address.");
                break;
            case "1":
                return gettext("Block added successfully");
                break;
            case "":
            default:
                return gettext("Failed to create block rule, alias, or add entry.");
                break;
        }
    } else {
        return gettext("Tried to block but had no address or interface");
    }
    return gettext("Unknown block error.");
}