No doubt.
First of all, Czechs stole that land that was granted to Poland in 1919. Second, knowing that the Nazis were about to move into the rest of Czechoslovakia, the Poles took those measures to protect the Polish majority living in the Cieszyn region. And by that time, Czechoslovakia had pretty much ceased to exist as an independant state. Granted the events of September 1939 made it a moot point.