The eldest child of Ludwig and Berta (née Schönbeck) Wallach, Käte Wallach was born in Krefeld on May 17, 1905. Her brother Ernst was born in 1909. Her father (b. Duisburg, 1876) was partner in a silk wholesale firm. No longer acceptable as a partner after the Nazi seizure of power, he managed to find work with the firm of Blankenstein until it went bankrupt in 1934, but later he had even greater difficulty in finding work. Käte Wallach described her parental home as democratic; both parents were convinced supporters of democracy as the desired constitutional form of government and therefore of the Weimar Republic.

Käte Wallach attended a high school for girls in Krefeld. After the family moved to Berlin she attended a Lyzeum in Dahlem, where she passed her final examinations in 1921. However, since the school education customary for girls in her time did not satisfy her, she decided to attend the classes established by Helene Lange which were at the time given by a Mrs. Strinz. In 1923, when the classes had to close because of the difficult economic situation, Käte Wallach switched to another gymnasium, where she passed the Abitur in September 1924.

After studying law for ten semesters at Berlin, Freiburg, Würzburg and Bonn Universities, she passed her First State Examination in January 1930 at the Court of Appeal in Cologne and began the legal training required to pass the Second State Examination at the Kammergericht in Berlin. She was first articled at the law office of Richard Becker and later, beginning in November 1930, at the prosecuting attorney’s office in Cologne. At the same time she attended Cologne University as an auditor in order to complete the two additional semesters required for being accepted as a Ph.D.  student there. At the end of the year she submitted her thesis on “Invalid dismissals in German industrial law,” supervised by Professor Hans Carl Nipperdey (1895–1968). She took the professional examination in July 1931. After the law of reestablishing the German civil service was passed in 1933, Käte Wallach and other Jewish colleagues were discharged by the state. Since she had almost completed the three years of her legal training, she was allowed to take the Second State Examination, which she passed in the autumn of 1933. However, she was not allowed to start work as an assessor or a lawyer.

After a kind of apprenticeship in a commercial company, she worked for a year in the advertisement department of a wholesale paper company, but at the first possible opportunity returned to the law office of Richard Becker as a senior clerk.

At the end of 1935 Käte Wallach emigrated to the United States with a temporary visa and with the help of the International Migration Service and the National Council of Jewish Women. She trained as a stenographer, taught German and worked as a secretary in various companies. In September 1936, having applied unsuccessfully for scholarships to study law once more, she started to work without pay for a patent lawyer in order to gain insight into the American legal system.

In 1937 Käte Wallach moved to New Haven, where she was offered work as secretary to Harry Shulman, who taught law at Yale University and who urged her to attend classes in order to see what she might like to do later. In the two years of working for Shulman, her interest in law grew so dramatically that she ignored all advice not to study law again.

She enrolled at the University of Wisconsin in Madison, where her good grades won her partial exemption from tuition fees and where she later finally won a scholarship. In June 1940, after studying only two years instead of the usual three, she graduated with an LL.B. as one of the best in her class. She was admitted into the Order of Coif, an honorary fraternity for lawyers which admitted only the best ten percent of graduating students. In her final year she was also honorary editor of the Wisconsin Law Review. In February 1940 she was admitted to the Kappa Beta Phi sorority.

Käte Wallach spent the summer of 1940 at Columbia University summer school in librarianship in New York City, in order to prepare for her new position as a cataloger in the law library at Michigan University at Ann Arbor. Besides her work as a cataloger she deepened her knowledge of librarianship by taking two more classes every semester at Michigan University. In May 1942 she received a B.A. in library science. The experience of working in one of the most renowned and best-equipped law libraries in the world shaped Käte Wallach professionally for her future in international, civil and comparative law. In July 1942, she became a US citizen.

For several years Käte and her brother Ernst, who had arrived in the United States in 1937, discussed the advantages and disadvantages of getting their parents out of Germany. None of them seemed aware of the full extent of the danger to which the parents were exposed. Only in 1941 did the children invest all their efforts in trying to help their parents escape. Ludwig Wallach died of a heart attack in 1941, and after January 1942 the siblings no longer received word directly from their mother or grandmother. In March they received a letter via the Red Cross. On August 27, 1942, their mother and grandmother were deported to Theresienstadt. where they died.

After graduating in library science Käte Wallach also passed the bar examination of Wisconsin in 1942 and was admitted at court. For four years she worked as a lawyer in Washington, D.C., first for the Office of Price Administration and later for the National Labor Relations Board. From 1943 she was also a member of the Wisconsin State Bar Association. At the end of World War II Käte Wallach was employed as an adviser on the international legal aspects of war crimes, particularly civil crimes.

In 1947 Wallach returned to librarianship. She declined the offer of a good position as assistant professor at the University of New Mexico and instead took a lesser post as a librarian at the University of North Carolina in Chapel Hill, in order to stay with the friends she had already gained.

In 1949 she moved to Baton Rouge to take up a post as assistant professor in the law school at Louisiana State University. In addition to teaching, she worked as a librarian. At the time she started work at Baton Rouge, the law library had 75,000 books. When she retired in 1975 they numbered 205,464. Her work was characterized by the collection of important books on all legal topics. Because she knew five languages, she was aware of new publications in all of them and thus established a main emphasis on foreign and comparative law at the library. Furthermore, she became very productive in her own academic research. In 1955 she published her most important work, the Bibliographical History of Louisiana Civil Law Sources, followed in 1958 by Research in Louisiana Law and in 1971 by the Union List of Basic Latin American Legal Materials. She also published over forty essays. In 1964 she was appointed to a chair and in 1966 she received a second doctoral degree, the JD, Doctor of Law. Four years later she resigned from administrative responsibility for the law library, but remained librarian for comparative law. As a teacher she was able to awaken interest and enthusiasm for comparative law in her students.

Käte Wallach was a member of the Soroptimists; in 1951 she became director and in 1954 president of the club. In 1955 she was admitted into the law fraternity Phi Delta Delta and later became its county president. As a member of the American Association of Law Libraries she functioned for over two years in two important posts: in 1951/52 she led the committee on educational issues, and in 1952/53 that for librarian education. From 1958 to 1959 she was president of the Southeastern Chapter of this institution, and from 1966 through 1967 president for the entire country. She also held a number of time-consuming honorary posts in the Association of American Law Schools and was vice-president of the Louisiana Library Association in 1959–1960, president in 1960–1961 and past president in 1961–1962. Her election to the presidency was a major topic in the media. Not content with all this, she was also a member of the American Society of Legal History, the American Bar Association, the University of Wisconsin Law Alumni Association and other bodies.

In her leisure time Käte Wallach liked to hike. Like many Europeans, she travelled with joy. As in her youth, she still played the piano and greatly enjoyed chamber music. She liked to visit museums. But her greatest passion, from childhood on, was reading.

When Käte Wallach retired on July 1, 1975, her work was honored in the headline of Baton Rouge’s daily newspaper: “Law Professor Never Settles for Anything But the Top.” On December 27, 1979, she died of cancer at her home in Baton Rouge.

“Nichtige Kündigungen nach deutschem Arbeitsrecht. Ein Beitrag zur Lehre vom Bestandsschutz des Arbeitsvertrages.” Diss. Köln: 1931.

“Designations of Super-employer Unit under National Labor Relations Act.” Wisconsin Law Review (1940): 556–567.

“Postwar Problems of the Law Library Equipment and Quarters.” Law Library Journal (1948): 329–334; Manual for Legal Bibliography. Baton Rouge: 1951.

Oil and Gas Bibliography. Baton Rouge: 1953.

Bibliographical History of Louisiana Civil Law Sources. Baton Rouge: 1955.

Research in Louisiana Law. Baton Rouge: 1958.

Union List of Basic Latin American Legal Materials. South Hackensack, New Jersey: 1971.

Louisiana American Legal Research Manual. Baton Rouge: 1972.

Co-Author of Comparative Coastal Zone Management. Baton Rouge: 1977.