Thanks everyone for their input. I was relieved to read Lena's take! Thanks for that

... when you're living the topic its hard for it not to be emotive. I'm going to try to keep this short! I'd also like to support Nicky's comment that one can be passionate about playing for ones country, but practicalities of reality can mean that either you move teams or sit out international comps... I left my home country in 2001 and have been on the move ever since. With some of the suggested solutions people have made, I would never have experienced a worlds.... my uwhockey (and my life!) would have been all the poorer without those experiences...
I think it is generally agreed that there is much more honour associated with playing for one's own country, and I would expect that it would always be a persons first choice. I have been in the unfortunate position of playing against my country of birth and this is very difficult (made easier on the first 2 occasions by having tried to play for them but not making the team). Switching allegiance is not easy, but if it's switch or not play and you're dedicated to playing and training then the decision is made easier. I love playing hockey and will try to play whenever I can, wherever I am....
I guess I'm not of the opinion that stepping down between wolrds is a great idea and also a one way gate sounds awful to me! When I have moved it was not to emigrate, but because of work related opportunities...while living and training in Aus I was grateful to be able to trial & play for them... but I hope one day to be back in my home country and it would be be awful to have a rule not allow me to try to play for them ever again!
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I'd like whatever the rule ends up being to allow for everyone who cuts the grade to be able to play - in a fair way (so, yes, definitely have clear rules). If you're living somewhere then I think you should be able to play for either that country, or for your country of origin. It is valid that a weaker player of that country will not play because the 'foreign' player has taken their spot... but what if the 'foreign' player has no other options. Is this the price they must pay for living outside of their country (yes?)