This is in response to both this discussion and the locked one on teleport traps
>>>here<<<In the discussion on teleport trap, the question is asked whether or not you can use a mandatory spell without the trigger occurring, which this thread on Nullify has answered in the affirmative (at least for the time being).
With the case of teleport trap, it is possible to cast it into a zone and then have a creature appear in the zone WITHOUT entering the zone, via a spawnpoint (FAQ page 9). Thus, the trap would not be triggered. However, if we could then voluntarily choose to use the enchantment, like the Nullify decision implies, then the creature would still be teleported.
And if we can voluntarily use these spells, why wouldn't we be able to use teleport trap to teleport our own creatures? The target for the effect of the spell is "that creature" meaning the creature that triggered it. This would imply it cannot be used without being triggered at all. However, the target for Nullify is "that spell" meaning the spell that triggered it. This would imply it also cannot be used without being triggered. Since we have been told that it can be used voluntarily without the trigger, it raises questions as to what "that spell" actually means.
An "incantation or enchantment spell controlled by an opponent" is merely what triggers Nullify and not what Nullify counters. "That spell" is what Nullify counters. If we allow it to be used voluntarily against a spell of our choosing "that spell" becomes any spell, including equipment, conjurations, and attack spells. Similarly "that creature" for teleport trap could be any creature, including our own.
Allowing mandatory spells to ever be revealed voluntarily would open a huge can of worms. Although I originally appreciated the tactical options it would allow, I think it is not worth the trouble and should be always mandatory. I still don't like the idea of time travelling to a previous step or skipping ahead to the next step, however. I think Reverse Magic can be rewritten to where it triggers Nullify within the Counterspell Step.