By Wojciech Kosc in Warsaw The decision by the German government to introduce tighter border controls as measure to curb migration is “unacceptable,” Poland’s Prime Minister Donald Tusk said on September 10. The apparently temporarily tightened border control regime kicks in on September 16, including along the nearly 500-km long Polish-German border. The border is an internal EU border covered by the free movement regulations, commonly known as the Schengen rules. Poland watches over hundreds of kilometres of EU’s external borders with war-torn Ukraine and hostile Belarus and Russia. Those bo…