Things sure are screwed up with the borders. They stop a 2 ounce houseplant at the border but let 200 tons of pot drive right through.
Agriculture has a duty to inspect incoming fruits, nuts and flakes (look out, San Francisco) for any kind of pests that could ruin our agriculture and thus our economy. I don't know what the story is with EggsAckley's seeds, and I hope it's resolved quickly, but it is routine to check such things.
Believe me, we don't "let" pot drive right through. We look for it, find it, and confiscate it. Sometimes we miss it, but it's definitely not deliberate when we do.
We make seizures all the time, it just doesn't make the news. Had a huge one in Blaine of crystal meth coming from Canada just a few days ago... did anyone outside of Blaine hear about that?