This deal occurred in an ACBL Grand National Teams club game. East's second bid was actually an insufficient 2♣, not accepted by South and corrected to 2♠, preventing West from bidding further. No calls were alerted.
At the end of the play, I was called back to the table. A result of +170 to E-W had been agreed, but West claimed that the South hand had failed to alert a negative free bid. A non-forcing 2♥ is alertable in the ACBL. North and South refused to admit at the table that this call was unusual for their partnership and argued that the extra length in hearts made the call OK, albeit lighter than expected. Away from the opponents later they claimed 2♥ was a mistaken bid and that what they were trying to say was that the South player had the right to make a non-system bid. Had West not doubled, North would be forced to make a call, they now claimed.
In the meantime I had ruled that they had an implicit agreement that 2♥ might be weak, evidenced by the hand, their comments at the time, and the rest of the auction, in which North chose to sell out to 2♠ with an opening hand opposite a free bid. I ruled it likely that West would choose 3NT with this knowledge and make it for +600, and found this to be also the most unfavorable result that was at all probable for N-S had the implicit agreement been known. Since N-S at the other table was +500 in 4♠ doubled, this turned a +12 into a +15 in IMPs, making the ruling itself responsible for a single VP.
1) Is there enough evidence here to make the ruling that N-S have the implicit agreement that free bids can be quite weak?
2) How much evidence does a TD need to assume an implicit agreement?
3) If I had decided that the 2♥ call was a mistaken bid and let the score stand, what should happen to the pair the next time this (or something similar) happens?
4) What can a TD do when a player makes a non-system action that works, such as an underbid or a strange choice of lead, and the opponents claim that the player or the partnership does this sort of thing quite often?