From 1927 onwards, Frank made a lightning career within the ranks of the N.S.D.A.P. That year, the party district Berlin was looking for lawyers to defend members of the N.S.D.A.P. in court. Frank handed in his application, became a member of the party and evolved within the shortest time possible into the star lawyer of the Nazis. Up to the seizure of power in 1933 he represented the party in a large number of cases. He represented Hitler in court about 150 times.
Frank defended his party chief not only in court. In 1930, rumours went around that Hitler was of partly Jewish ancestry. He ordered Frank to start an investigation into his family history. After the war, in his cell in Nurnberg, Frank wrote his investigation had revealed that it was not unthinkable that Hitler’s father had been half Jewish. Hitler’s unmarried grandmother, Maria Anna Schicklgruber would have given birth at the age of 42, to a child out of wedlock, Hitler’s father, out of a relationship with a 19 year old descendant of the wealthy Jewish Frankenberger family for whom she had worked as a cook. Frank discovered that the Jewish family had paid for the upbringing of this child until it had reached the age of 14 but at the time, he came to the conclusion that this only had been done to support the mother financially. The child would have been fathered by one Johann Georg Hiedler, a miller’s hand who was the second cousin of Maria Anna Schicklgruber. Four years after the child was born, he married her and changed his name to Hitler. That at least was the official version created by Frank. The influential biographer of Hitler however, Kershaw, discounted Hitler’s Jewish ancestry as unproven and highly unlikely, if not impossible.
Frank was not only interested in the juridical practice but also in the theoretical aspect of Nazi law. He founded the Bund nationalsozialischtisdcher Deutscher Juristen (Association of German Nazi lawyers), renamed the Reichswahrerbund in 1936. He also was appointed chief of the legal department of the Reichsleitung N.S.D.A.P., which from 1935 onwards was called the Reichsrechtsamt (state legal agency). In addition, on October 2nd, 1933, Frank also became President of the Akademie für Deutsches Recht (Academy for German law). This institution was to prepare a radical legal reform based on National socialistic ideas. This provided the academy with far reaching powers to co-ordinate the legal base of the whole German empire. According to its charter, it was the task of the Academy to "promote the rejuvenation of written law in Germany and the realization of the nationalsocialistic program concerning written law". Frank left no doubt as to what that would mean to those who thought otherwise and to Jews.
Excerpts from a speech on radio on March 20th , 1934: "A fundamental principle of law is the legal elimination of those political organisations that used to have the opportunity within the state to place their own egocentric goals above the general well being of the nation. In the meantime, this elimination has been carried out legally. This does not emerge from despotic leanings but it is the necessary legal consequence of an obvious political result, namely 14 years of struggle by the N.S.D.A.P.
The same speech included a threat that could not be misunderstood: "Another basic principle is racial law. The National socialists were the first in the history of legislation to raise the racial concept to the status of of legal concept. The German nation, racially and nationally unified will in future be protected by law from further disintegration of the pure Germanic race"
A good listener could already draw the conclusion: there was no place for Jews in law. For those who still harboured doubts, in a speech on October 3rd, 1936, Frank left no misunderstanding: "In particular, we national socialist lawyers have our own mission. (…) We will build German law on the old and vital foundations of the German people (….) It is so abundantly clear that it hardly needs to be said: any participation by Jews in German law is impossible. The elimination of Jews from German jurisdiction is not due to hate or envy, but to the fact that the influence of the Jews on German life is in essence harmful and pernicious and that an unmistakable line must be drawn between us and the Jews in the interest of the German population and its future".
Nazi theoretician Frank also let himself be noticed in practical politics. In 1930 he won a seat in the Reichstag for the N.S.D.A.P. and following the seizure of power by the Nazis in 1933 he was given a few political functions. On April 18th, 1933, Frank was appointed Justizminister (Minister of Justice) in Bavaria and on April 22nd, his appointment as Reichskommissar für die Gleichschaltung der Justiz in den Ländern und für die Erneuerung der Rechtsordnung (Statecommisioner for the standardization of the law in the federal states and the renewal of jurisprudence). In this function he was to impose Nazi legislation on the whole empire. He set about this task so energetically, he soon made himself redundant as Bavarian Minister of Justice; after all, after the standardization of the legal system in all regions of Germany, individual ministers of Justice had become superfluous. The standardization also meant the end of his work as Reichskommissar. The goal had been achieved.
In December 1934, Frank resigned as Minister of Justice of Bavaria and his task as Reichskommissar was completed. His resignation may also be in connection with some critical remarks, he had made in this function. For example, earlier on, Frank had complained about illegal executions that had taken place in concentration camp Dachau. Moreover, he did not agree with the liquidation of high ranking members of the SA in June 1943 in the Night of the Long Knives. Whatever it may be, after 1934, Frank lost all effective political influence in Germany. Indeed, he became Reichsminister ohne Geschäftsbereich (Minister without Port folio) and would remain so until the end of the war but this hardly carried any authority. Apart from that, he held a number of representative posts in the party such as being one of the 18 Reichsleiter of the N.S.D.A.P. who formed the party leadership. However, his political role in Germany was almost over. It did not mean though that he permanently faded into the background. In 1939, Hans Frank would be called upon to perform a very different task in occupied Poland. With this he would definitely establish his dark reputation in the history of the Second World War.