Rule3
Eons ago, 25 or more extremely experienced Australian Approach and Tower Controllers went to work in Hong Kong for the opening of the new airport.
Most had asked for 3 years leave without pay and were denied.
MisManagement thought we wouldn't go, and got a very rude shock when we did.
Yes, and I understand that ASA sent a senior manager to Honkers to stem the tide. It didn't work.
ANSPs had unwritten "no poaching" agreements but this has changed over the last decade or so, especially as some ANSPs do little or no training of ab-initios.
I'm surprised that Airservices haven't paid Airways to do their "top-up" training (to guarantee 100 rated ATCs each year) and/or a "loan" scheme of rated controllers working in Australia for 3-5 years.