In canon it's written on a youkai contract, though what power that entails has never been answered by ZUN. At the very least it gave Byakuren and Miko (and notably not Yorihime) knowledge of the rules despite being locked away for about 1000 years before Gensokyo existed. It's most likely not magically enforced as Sumireko, who doesn't know the rules, wasn't punished for pulling out a gun. Impossible Spellcard does show that a lot of characters have "impossible" spell cards so that could be a way to counteract cheating without cheating yourself.Whenever I try to imagine who actually enforces these rules, the conclusion I usually end up landing on is that if you don't play by the rules, they're gonna kill you.
It is enforced through threat of lethal violence. And we assume there is a social contract going on – that most people agree that these rules keep Gensokyo together, and they should work together to keep it that way and help with correcting people with funny ideas.
I think... impossible spell cards might be a fatal flaw of the dueling rules. Because paradoxically within the context, they are beautiful, yet they are also too strong for an average duel. I suppose it depends on the duelist herself to judge whether her spell cards are possible or not? Would it be a common occurrence, then, for a spell card to be deemed impossible by many opponents even though the duelist herself believes otherwise? How do we tell if it's not just "skill issue"?In canon it's written on a youkai contract, though what power that entails has never been answered by ZUN. At the very least it gave Byakuren and Miko (and notably not Yorihime) knowledge of the rules despite being locked away for about 1000 years before Gensokyo existed. It's most likely not magically enforced as Sumireko, who doesn't know the rules, wasn't punished for pulling out a gun. Impossible Spellcard does show that a lot of characters have "impossible" spell cards so that could be a way to counteract cheating without cheating yourself.
Impossible Spell cards are basically lifted ruling for a manhunt against a Seija. It was limited to Seija and Seija alone, you must have pissed the whole council if they decided to lift the rules just for you.I think... impossible spell cards might be a fatal flaw of the dueling rules. Because paradoxically within the context, they are beautiful, yet they are also too strong for an average duel. I suppose it depends on the duelist herself to judge whether her spell cards are possible or not? Would it be a common occurrence, then, for a spell card to be deemed impossible by many opponents even though the duelist herself believes otherwise? How do we tell if it's not just "skill issue"?
Keeping things vague breeds creativity, but the spell card rules just churn out more and more questions that I'd almost rather assume it's just regular fighting with move-shouting and call it a day.