The Cliff's notes version of the story is that in the 90's, Jerry Irvine A) got into a feud with Tripoli leadership and B) got into legal trouble for shipping motors against DOT regulations and lying about it. NAR and Tripoli refuse to certify his motors and Tripoli refused to allow him to rejoin as a member. Therefore none of his motors can be flown at any TRA or NAR launch, as research motors, commercial motors, or anything else. Depending on your state, use or possession of them may be against the fire code due to being uncertified.
That said, his kits are good, and he continues to be involved in making motors for TV and other applications where NAR or Tripoli certification is not required. He tends to be vilified within some TRA circles, partly because it's the nature of clique-ish groups to pick on outcasts, and partly for bad behavior on his part, most recently including forum posts that got him banned at TRF and Rocketry Planet. I think it's too bad that he and the national rocketry organizations can't get along, because he probably still has a lot to offer the hobby if he could be more involved.