His videos of making them were on YouTube for years, publicly. It's legal to synthesize the explosives he made. What they did was charge him for the first amendment protected activity that a terrorist then found, and then they claimed that because he made some money because a few people donated a small amount to him for making the videos, and thus he needed a commercial license for being in the business of making explosives.

By the way this is the same thing they tried to charge FPSRussia (the first time, before they convicted him for weed) for and failed.