shell management makes a valid point
US Visa and Immigration law is tough (and rightly so) in order to protect the interests of US workers, try going over to US and starting up as freelance instructor you will soon get a visit from the authorities and you will be on a plane back to whence you came (unless you have green card or citizenship)
Might be time to do the same for Europe (after we make it easier for pilots to gain IR etc of course) in order to compete and protect our own citizens rights and jobs.
Not such a daft rule perhaps ?