There was only one loophole: the port city of Shanghai. The Japanese invaded Shanghai in August 1937, driving out Chinese government authorities, which left the harbor unmanned. The other foreign powers in the city did not want the Japanese to take over the harbor because it would "inconvenience" them. So, the harbor was left completely unattended, without passport control or immigration. Anyone could land without showing papers or passports.
My father took advantage of this situation to issue entry visas with an end destination to only one place in China — Shanghai — which actually required no visa to enter.
This was my father's "Shanghai visa strategy", his intentional off-label use of a normally standard entry visa. Armed with these Shanghai visas as "proof of emigration", Jews were allowed to leave by the Nazis, and their imprisoned relatives were released. The Shanghai visas could also be used to enter otherwise inaccessible countries on the pretext of transiting through them on the way to Shanghai.
My father himself said: "These visas are to Shanghai in name only. In reality, they will provide a means for Jews to find their way to their preferred destinations."