The auction at my table started (South dealer):
...P....1♣....1♠....1♥
I (North) pointed out that this was insufficient, and as I was the director and the only person in the room who had any chance of giving a decent ruling, set about the matter myself. I said that South would have the option of accepting the insufficient bid, but if he didn't want to, assuming both 2♥ from East and whatever East intended with 1♥ were natural, East could....
Before I could get round to listing East's options (including probably a penalty-free negative double), South announced he didn't want to accept it and East bid 2♥. This was passed out and defeated by one trick for a NS top.
West's decision to pass what would ordinarily be a forcing bid (they don't play, indeed, have never heard of, "negative free bids") turned out badly for their side, but suppose it hadn't? If it had been the winning action, would NS have been due any redress?
I have my views on this, I just wanted to see what other people think.