Well, I don't really believe that licensing is too much of an imposition upon our 2nd amendment rights (and I am very pro-2nd amendment and a gun owner myself). As with all bill of rights provisions, there have always been limitations (a prime example would be fire in a movie theater concerning free speech). Anyway, I feel licensing may not be too unreasonable of a restriction on weapons sales. Its when the restrictions become an arbitrary burden on those trying to obtain firearms that I feel Due Process of the 14th amendment and the right to bear arms of the 2nd amendment are being infringed upon (check out substantive due process upon legislation concerning a wide array of issues). Anyway, I don't feel like this instance was too imposing on people's rights (but then again, I don't know all the details concerning this specific story)
Let me further add that anyone arrested for buying these weapons, not knowing the dealers were unlicensed, should not, and most likely will not, be persecuted.