As I read the court's decision, the issue was whether the defendant carried a weapon concealed upon his person. The court held that in a backpack is not upon the person. In the final lines of the decision the court mentions that had the defendant been charged with possession of shuriken instead of dirks & daggers, the conviction may have been upheld since that is controlled by a separate part of the statute that outlaws possession of shuriken. The actual weapons found on the defendant were shuriken and not dirks or daggers.
Blogger missed some of the point of the court's decision...
Even if the weapons were swords in real life, for our purposes here, the weapons were
actually dirks or daggers because that is what the lower court found. See, Appellate Opinion at page 2:
http://www.courts.ca.gov/opinions/documents/B238949.PDFHe was initially found guilty on possession of dirks or daggers. The note about how the weapons could have been shuriken is interesting but irrelevant. I suppose the weapons could have been spears. That would have been interesting too, but it doesn't matter because the courts treated the weapons as being dirks or daggers.