Imprisonment
With clear lines drawn after Terboven's speech, Hjort withdrew from party politics for the last time and devoted all his time to law. With his knowledge of German affairs, he was a resource for other Norwegian lawyers. There were many cases when Norwegian resistance fighters needed defence counsel. It was a legal voyage through increasingly troubled waters; the Supreme Court was dismissed, and the occupation forces were constantly pushing for lawyers to adapt to the new conditions. He also held lectures in the German-controlled Norwegian Broadcasting Corporation, alongside individuals like Albert Wiesener, Jonas Lie, and Ranik Halle.
In January 1941, the Norwegian Bar Association was pressured to include an article in the Norwegian Legal Gazette on "The development of constitutional law in Norway" by Rudolf Schiedermair, Terboven's legal adviser. Hjort took it upon himself to write a response with the assistance of other Norwegian lawyers and Frede Castberg. Hjort's response was diplomatic in form, but nevertheless ruthless when Hjort concluded that the Germans had violated international law by their conduct during the occupation, and that Quisling had committed a coup d'état.
Hjort must have known what such public criticism of the occupying forces would lead to, and he was arrested on 21 October 1941. Hjort was first detained at Møllergata 19 (Oslo's main police station at the time) and then transferred to the Grini prison camp in December 1941. The time in solitary confinement at Møllergata 19 was a difficult period for Hjort, but the community at Grini with many acquaintances made his imprisonment easier. In fact, many of the most important of the Norwegian social elite were at Grini. After the liberation, it was seen as a badge of honor to have been imprisoned there. From then on, Johan Bernhard Hjort was definitely considered to have been on "the right side" of the war.
In Germany, his brothers-in-law tried to get him released, and Rüdiger was allowed to meet Terboven in November 1941. But the German Reichskommissar was outraged and stated: "The pig sits down and writes an article" (German: "Das Schwein setzt sich nieder und schreibt einen Artikel".) Hjort's attempts to speak out against the occupation forces were not taken kindly. At the same time, his arrest was also linked to his brother-in-law Johan Holst's escape to Sweden.
On 6 February 1942, Hjort was sent to Germany on the prison ship "Donau" and placed in the prison at Alexanderplatz in Berlin. Hjort's brother-in-law Rüdiger approached Himmler, and the SS commander was open to an agreement that resulted in Hjort being released, but having to stay in Germany with his family until the end of the war.
In May, Rüdiger was allowed to meet Hjort to explain the conditions, but Hjort's family in Norway, Anna Cathrine and the six children were reluctant to settle in Germany.
Anna Cathrine Hjort was allowed to meet her husband in Berlin, but she and the children were equally dismissive. There were rumors and many people believed that Hjort was now willing to cooperate with the occupiers. Hjort was released, but in so-called civilian internment. Rüdiger got him a job as a legal consultant in the oil company Continentale Oehl Gesellschaft in Berlin. By October, after strong German pressure, the family had given in and settled on the Gross Kreutz estate in the village of the same name 20 km west of Potsdam. The estate was owned by Hjort's cousin Bodo von der Marwitz.