I suppose there's a good reason for importing roundworms

Yes. These specific worms (Caenorhabditis Elegans) are incredibly important in biological research - apparently they're the source of countless research projects. Here's a brief description from the University of Minnesota's Caenorhabditis Genetics Center, which is an entire research group in that university devoted to studying them:

cgc.umn.edu - What is c elegans

You understanding this factoid promotes the Up to No Good hypothesis, yes?

Yes - I fully believe they were Up to No Good. Importing prohibited animals on purpose - whether because you want to do research without complying with laws, or because you want to make money on black market pets - is Up to No Good. "Up to No Good" is not the same as "deliberately trying to cause bioterrorism." Clearly these guys were trying to source the specimens they wanted for their research without having to follow the rules. Which is No Good! Animal control rules are there for a reason, and it can be devastating if you don't follow them - whether you're importing C. Elegans for your research or a tanuki just to have as a pet!

But it's not bioterrorism - and you can bet your bippy that if there was even the merest hint of a whisper of a suggestion that these guys were importing these things for bioterrorism, and not just willfully breaking the rules so they could do their research, then they would have been charged with a terrorism count.