Ah.. Didn't think about regulations just technology

But if it must use that cross-cable you should verify if it really does use that connection and not the one via the router. One way to do it would be to install something like wireshark and sniff the traffic on the cross-cable connection. That would quickly determine which NIC gets used. Unplugging the cable could be an option too but there's a risk the application will still work because it would 'silently' switch to the other connection.