Following a month-long series of attacks by members of the SA on Jewish businesses and synagogues, on 1 April 1933 Hitler declared a national boycott of Jewish businesses.[294] The Law for the Restoration of the Professional Civil Service passed on 7 April forced all non-Aryan civil servants to retire from the legal profession and civil service.[295] Similar legislation soon deprived other Jewish professionals of their right to practise, and on 11 April a decree was promulgated that stated anyone who had even one Jewish parent or grandparent was considered non-Aryan.[296] As part of the drive to remove Jewish influence from cultural life, members of the National Socialist Student League removed from libraries any books considered un-German, and a nationwide book burning was held on 10 May.[297]