Complex sentence: Brothels are illegal de jure but in practice they are restricted in location to certain areas of any given town and thus although the profession does not have official sanction, little effort is made to stamp it out or to take action to impede it.
Split into simpler sentences: Brothels are illegal "de jure", but in practice are restricted in location to certain areas of any given town. Although this profession does not have official sanction, little effort is made to stamp it out or to take action to impede it.