It was the prevailing opinion at the time, and many compnies, some state-owned, have and do own patents on plants and their derivitive compounds. While its possible laws and treaties existed then, I am unaware of, I understand it was a literal trade secret, that had been stolen. It would not be hard to interpret that as theft (literal; of seedlings, or monetary; by damages) regardless of precedent. I know contries are still very protective. https://www.desmoinesregister.com/story/news/crime-and-court...

Just opinion... this kind of theft predates current law, though. Think of the silkworm smugglers [1] as well. Some crops an agri/zoo cultures were considered strategic resources and tightly controlled by the state. No idea what current international law says about stuff like this.

[1] https://en.m.wikipedia.org/wiki/Smuggling_of_silkworm_eggs_i...