Why at start for some devices ret = libusb_open (dev, &handle) Returns error status code <LIBUSB_ERROR_NOT_SUPPORTED>?

Example: static int print_device (libusb_device *dev, int level) { struct libusb_device_descriptor desc; libusb_device_handle *handle = NULL; char description [260], string [256]; int ret; uint8_t i;

ret = libusb_get_device_descriptor (dev, &desc);
if (ret <0) {
	fprintf (stderr, "failed to get device descriptor");
	return-1;
}

ret = libusb_open (dev, &handle);
if (LIBUSB_SUCCESS == ret) { // Ok!
}
else {//error!!!
	snprintf (description, sizeof (description), "Err: %04X - %04X", desc.idVendor, desc.idProduct);
}

................... }

I use Win7 x64.