Naturalization, on the other hand, also proved to be a…

““Naturalization, on the other hand, also proved to be a failure. The whole naturalization system of European countries fell apart when it was confronted with stateless people, and this for the same reasons that the right of asylum had been set aside. Essentially naturalization was an appendage to the nation-state's legislation that reckoned only with "nationals," people born in its territory and citizens by birth. Naturalization was needed in exceptional cases, for single individuals whom circumstances might have driven into a foreign territory. The whole process broke down when it became a question of handling mass applications for naturalization: even from the purely administrative point of view, no European civil service could possibly have dealt with the problem. Instead of naturalizing at least a small portion of the new arrivals, the countries began to cancel earlier naturalizations, partly because of general panic and partly because the arrival of great masses of newcomers actually changed the always precarious position of naturalized citizens of the same origin. Cancellation of naturalization or the introduction of new laws which obviously paved the way for mass denaturalization shattered what little confidence the refugees might have retained in the possibility of adjusting themselves to a new normal life; if assimilation to the new country once looked a little shabby or disloyal, it was now simply ridiculous. The difference between a naturalized citizen and a stateless resident was not great enough to justify taking any trouble, the former being frequently deprived of important civil rights and threatened at any moment with the fate of the latter. Naturalized persons were largely assimilated to the status of ordinary aliens, and since the naturalized had already lost their previous citizenship, these measures simply threatened another considerable group with statelessness.””

— Hannah Arendt