Legality of the telescopic batons in a bit controversial issue in Poland.
According to the law you need a permit for:
the batons/sticks with an end of the heavy and hard material, or containing inserts from such a material
So the issue might be the plug at the end of the telescopic baton. But it's not heavy at all (this plug) and has the same diameter as the stick, so most experts claims that the permit for such baton is not needed. See this article (in Polish unfortunately)
Of course you may be checked by some city guards in Poland and questioned however it's clear that your intention is just training and not to hurt another person - especially your own wife.
I think if you are training in a club, then some card or certificate would be helpful too.