A lot of states have classified feral hogs as vermin or pests. As such, they are not protected by the regulations for other species of big game. That usually means no limits, no closed season, spotlighting allowed, few restrictions on public land and almost none for private land.
Even with all that, the hog problem is growing. If you want to make an impact on a hog population, shoot the sows, especially the unbred ones (gilts).