An economic union that involves the EU demanding Ukraine release people in prison? Are those not internal affairs for Ukraine? What business does Brussels have with the Ukrainian legal system?
I don’t know the details of the EU’s conditions for free trade, but it seems to me that (i) they are far less restrictive than the amount of control excercised by Russia over members of its “tariff union” and (ii) the wisdom of entering into such treaty should be up to Ukrainians, not Russians.