Why did one council vote in Lviv trigger a Schengen ban in Warsaw?

Regional councillors in Lviv voted to declare next year the year of the Ukrainian Insurgent Army and its commander, Roman Shukhevych. N-tv reports that the UPA carried out mass killings of the local Polish population in what is now western Ukraine.

Warsaw's presidential spokesman, Rafał Leśkiewicz, called the case outrageous. It smells of a Russian provocation.

Poland has barred Swiatosław Szeremeta, the regional councillor who proposed the resolution, from Poland and the Schengen zone for 5 years. Foreign Minister Radosław Sikorski requested the ban, and Interior Minister Marcin Kierwiński confirmed the decision.

In Wrocław, Law and Justice's Łukasz Kasztelowicz says: These actions are a blow to Poland. Kyiv's Foreign Ministry also calls the decision counterproductive, noting regional councils are not subordinate to central government, and urges Poland to avoid radical steps.