What happens if you cannot get online on launch day

Boring but real. Someone asked me this and I did not have a confident answer.

The game needs a licence check at first launch even for single player. If your connection is down on the 19th, or the store is unreachable, does the preloaded copy simply refuse to start?

My understanding is that once the check has passed once, you are fine offline afterwards. What I do not know is whether there is any grace period if it cannot reach the servers at all on the day.