From Slate:

If James succeeds, the court will direct her to find other groups who could take control of the NRA’s infrastructure, which could restart a national gun rights advocacy group. She would be bound by law to solely consider whether successor groups share the NRA’s values and are free from any taint of corruption. “The groups would have to be absolutely squeaky clean, but they could have really aggressive Second Amendment politics,” West said.
Though the NRA has defined the national gun rights movement for decades, it is by no means the only player on the scene. Rivals have grown in prominence in recent years. And many of the lesser-known groups are in fact much more extreme in their pro-gun stances, and closer to the far-right fringe.