Biography by Wikipedia, reproduced here for relative brevity and comprehensiveness:
Hans Calmeyer - Biographical Background
Hans Georg Calmeyer was born in Osnabueck in Germany on June 23 1903. He became a well-known lawyer working in a private practice employing two members of staff - one of whom was a Jewish woman. When the NSDAP (Nationalsozialistischen Deutschen Arbeiterpartei) came into power in 1933, he was briefly prevented from practicing law due to suspicions about his political beliefs that were assumed to be communist. This assumption was based on the fact that Calmeyer had previously defended communists in court. He was indeed more left-wing than right, but did not hold to any extreme political beliefs. With the climate as it was however, it took very little persuasion for those in power to label him as politically subversive.
However, he was eventually allowed to resume his practice when fears of his political extremes died down. So when Germany attacked the Netherlands in 1940, Calmeyer was installed as an adviser into the Reichskommissariat based in the Hague as a result of his knowledge of Dutch and his legal training. He now found himself in a position of some potential power. He realised that it would be unwise to openly declare his very real sympathies for the plight of the Dutch Jews that by this stage was becoming apparent. He only dared to speak of his hatred for the policies and beliefs of National Socialism to a select few friends - on the outside he maintained the pretence of an ideal citizen.
He avoided any contact with other lawyers who acted on behalf of Jews and this served to create an air of detachment from both the pro-nazi sympathisers and also those against National Socialism. He also avoided any attempt to act on behalf of Jewish clients himself. His new employees were carefully selected though - his assistant lawyers were both opposed to the Nazi regime and other office staff had similar leanings - all in all a work force that he could trust. Calmeyer's bureau became a singular anti-National-Socialist cell within the occupation government.
Proof of racial heredity
With this steady base in place, Calmeyer was able to look to his plans of aiding persecuted Jews and he used his legal expertise in this mission. German Nuremberg Laws stated that membership of a Jewish community was sufficient proof that an individual was Jewish - only the Fuehrer was capable of invalidating a person's Jewish descent or deciding that an individual could be taken as an exception to the rule. Calmeyer disputed this law in March 1941 in a memorandum. He claimed that within the framework of racial laws, one's membership of a religious community could not be regarded as a decisive factor. He also made the point that the practical application of this law seemed much stricter in Holland than in Germany where the law originated - he supposed that this was due to the absence of a supreme Dutch authority where such problem cases could be reviewed. He went on to demonstrate real situations where this law could not be seen to work - a prominent member of the Dutch National Socialist Party (N.S.B) who had a Jewish grandfather and an influential banker whose grandmother had been of Portuguese Jewish descent. Calmeyer therefore proposed that a different level of proof of origin should be entertained in Holland - which required more than just membership of a Jewish community.
Two seasoned lawyers, Dr. A. Seyss-Inquart and Dr. F. Wimmer, had the task of reviewing Calmeyer's proposal. By approving it, they were unaware that they had, in effect, created a loophole in the law allowing numerous Jews to escape persecution and probable death. As soon as the decision was passed, petitions began to arrive at Calmeyer's office from Jews requesting that the status of a parent or grandparent be changed from Jewish to half-Jewish or even to "Aryan". Proof of non-Jewish origin could be sought by obtaining a certificate of Baptism and where an authenticate copy could not be produced or was refused, a forgery could quite easily be made. Proving an illegitimacy (i.e. by having a grandparent who might be the illegitimate child of a Jewish mother and Aryan father) was another route - an official extract from the population register was required in this case although it has been documented that some people were willing to bend the truth somewhat to obtain a falsified document. Whenever doubts about a person's origins were successfully raised, deportations were postponed until further classifications could be made. The Germans were concerned about destroying precious Aryan blood, especially that of the Dutch, who were considered pureblooded Aryans.
Such certificates and documents to authenticate this proof of non-Jewish origin were issued by Calmeyer's office. However, Calmeyer himself, who was extremely correct and incorruptible never involved himself personally with forgeries. He did however spend much of his time adjudicating requests that he knew personally to be based on insufficient or non-existent evidence. In some cases he demanded anthropological examinations, which were performed by Professor Dr. Hans Weinert, a morphologist who invariably produced reports testifying to the non-Jewish physical characteristics of the applicant. The decision on whether to proceed with an appeal or not would be based on the likelihood of that case being examined by the authorities. Calmeyer still had to maintain a faade of compliance - so, he was cautious with the cases he took on - as a way of preserving his ability to help in future. He was already attracting suspicion from the more fervent Nazis who said his activities were genealogical fraud, and they begun to demand a case-by-case review of all of his approvals.
In early 1942, Ten Cate, an SS protege was appointed to the position of Official Representative for Genealogical Certificates. This was an obvious move against Calmeyer, Cate had assembled a collection of some 100,000 file cards containing information on Jewish subjects - and particularly those resident in the Dutch colony of Surinam. The threat of Calmeyer had obviously been perceived, but the authorities were unable to act in any significant way - Ten Cate was eventually dismissed in 1944 following a quarrel with other National-Socialist officials.
The SS made further efforts to kerb Calmeyer's activities. In March 1944, an order arrived from the RSHA (Reich Security Main Office) in Berlin demanding a closer examination of all Calmeyer's decisions, and, in August 1944, the request was made again. Calmeyer had also omitted to implement an order given in December 1942 forbidding him to take on new cases.
The Dutch Schindler?
It does not seem shocking that Calmeyer be labelled as a supporter of Jews by the pro-Nazi authorities. However, his rationality, perhaps an inherent trait of a man imbued with legal etiquette, meant that he maintained his status as an "untouchable". He underwent significant psychological pressure - meeting with the very men he secretly despised in order to aid those at risk.
In numerical terms, Calmeyer's interventions are impressive - out of a total number of 4767, he recognized 2026 as half-Jewish, 873 as Aryans and rejected 1868. We can also take into account that the descendants of those individuals cleared, were also automatically exempt. Each petitioner was exempt from deportation during the processing of their applications, allowing them the time to make plans of escape or disappearance should that route be necessary. The secretaries working in Calmeyer's office are said to have warned any petitioner whose case had been unsuccessful, allowing them to disappear before the authorities reached them.
Around 60 per cent of the applications passing through Calmeyer's office were successful - and most of these were based on forged or fictitious documentation. Calmeyer was therefore directly responsible for saving the lives of around 3000 Jews. His methods may have been understated and outwardly un-heroic but in the climate of the time, he had to assume a certain manner, contrary to his beliefs, in order to make a difference. Those 3000 perpetuate further generations. You cannot determine what quantity is valid when it comes to saving peoples lives. The fact is that he did, he didn't have to - life would have been easier for him if he had been subservient to the authorities - his resistance was of a particular type - he used his skills to the greater good and stood up for human rights.