There are a number of issues involving this topic.
1. Personally,I think that doing this would contravene European Law by restricting the number of countries any rider could race in. However, should a rider decide to sign a Poland contract with this fact written into it, I would imagine by waiving the right, he would be agreeing to abide by this. Therefore, Poland would not then be breaking any EU Laws.
2. I have always assumed that it is Poland and Sweden where a rider can reap the greatest rewards for his services. One fact I am not aware of the answer to, is whether it is mandatory for a rider to race in his own national leagues. Lets assume it is a Dane we are talking about. If he HAS to race in his countries leagues, he would then have to choose between Poland, Sweden and the UK (perhaps)for his other country to ply his trade. More than likely, he would opt for Poland above Sweden. By doing this, he would diminish his earnings, whereas as Swede would benefit by this arrangement.
3. We have seen two clubs, Poole and Wolverhampton, sign riders coming up to the Play Off stages of our Elite League. Whilst I don't agree with this, it was done legally within the existing framework of rules, so fine. Come next August, it would not be as easy to pull the same trick if a rider is riding under Poland's no more than two leagues contract restriction.
4. British leagues (Elite & Premier), have suffered from the lack of riders racing in the UK. This has resulted in riders racing in both leagues to make enough meetings available to justify the outlay for machinery. A Polish restriction could well reduce the number of riders available to both leagues . It would not surprise me if someone like Bomber Harris tried his hand at both leagues.
British speedway is not strong enough to start waving the big stick at Poland, if they did, I doubt much notice would be taken of it. The SGP, of which they get 3 rounds is a great coup for them. It would be nice if BSI took 2 of them away from Poland and awarded them elsewhere. Would they do that, NOT A CHANCE; and the FIM say they can do nothing about it.
We may well have to rely on our old friends from the Commonwealth and nurture our own talent. Do you agree or not?