Someone said, "I want to do this," and the government credibly responded, "Do that and we'll take action against you." This equals standing for pre-enforcement actions, because the government is threatening to do something. If the government had responded, "Go ahead, we don't care", then that someone would not have standing. You don't always have to wait for the government to actually take action against you to have standing, so long as you can prove the government would take action against you if you did the thing.