Demystifying Rulings, Part 11: Move Legality

[Stardog]

Can Fossil Dyna Pachycephalo be used for an Xyz Summon?
Fossil Dyna Pachycephalo’s effect (of interest) reads as follows:
Neither player can Special Summon monsters.

If we read it as “Neither player can ‘attempt to’ Special Summon monsters” then it becomes clear why you cannot use Fossil Dyna for a Synchro or Xyz Summon, or as a Tribute for a Special Summon – even though that those actions would remove Fossil Dyna from the field, you can’t even attempt them while Fossil Dyna is face-up.

If a Special Summon is negated, can Pot of Duality be activated afterwards?
Duality has this clause:
You cannot Special Summon during the turn you activate this card.

Again, the important factor here is whether a Special Summon was actually ‘attempted’ or not. Duality cannot be activated if a Special Summon was attempted that turn.

For Special Summons that do not occur while a Chain is resolving, whether the Summon is negated or not, the Special Summon is still attempted. So for example, even if an Xyz Summon is negated by Solemn Warning, Duality cannot be used later in the turn.

For Special Summons that occur during a resolving Chain, if the activation of the effect is negated, then the Special Summon was NOT attempted. Otherwise, the Special Summon is still attempted.

For example, suppose the effect of Summoner Monk activates:
Once per turn: You can discard 1 Spell Card; Special Summon 1 Level 4 monster from your Deck, but that monster cannot attack this turn.

If Solemn Warning negates the activation of Summoner Monk, then Duality could be activated afterwards. However, if Effect Veiler was used to just negate the effect, Duality could not be activated afterwards.

Gozen Match/ Rivalry of Warlords
Gozen Match reads as follows:
Each player can only control 1 Attribute of monster. Send all other face-up monsters they control to the Graveyard.

Rivalry is the same, but for Type.

Similar to Fossil Dyna Pachycephalo’s case, you cannot attempt to Xyz Summon, say, an EARTH monster using your two DARK monsters. That would be a direct attempt to control a different Attribute of monster.

There are several other rulings that are easier to understand by thinking in this way. The following is Konami’s article on these cards: [You must be registered and logged in to see this link.]

Principle of Costs
Let’s get straight to the principle of costs: “If you can’t pay the cost, you can’t activate the effect”.

Often, a card like Masked HERO Dark Law is to blame:
Any card sent to your opponent’s Graveyard is banished instead.

While Dark Law is face-up on your opponent’s side of the field, there’s no way to successfully send a card from your hand to the Graveyard.

Now let’s look at Effect Veiler:
During your opponent’s Main Phase: You can send this card from your hand to the Graveyard, then target 1 face-up Effect Monster your opponent controls; negate that opponent’s face-up monster’s effects until the end of this turn (this is a Quick Effect).

Effect Veiler’s cost is sending it to the Graveyard, but while Dark Law is face-up, if you were to try to send Veiler to the Graveyard, it would never get there. You can’t pay the cost of Veiler, so you can’t activate the effect at all.

If the card doesn’t specifically need to be sent to the Graveyard (eg. if it just needs to be Tributed or discarded) then its effect can still be activated.

Principle of Mandatory Effects
The mandatory effects principle is: “Mandatory effects always activate, unless explicitly prevented”. For example, the effect of Sangan to search the Deck when it is destroyed would still activate when Thunder King Rai-Oh destroys it by battle.
When this card is sent from the field to the Graveyard: Add 1 monster with 1500 or less ATK from your Deck to your hand.

Neither player can add cards from their Deck to their hand except by drawing them.

Of course, as long as Rai-Oh is face-up at resolution, Sangan’s effect will resolve without adding a card.

However, if Majesty’s Fiend is face-up, Sangan’s effect would not activate at all:
Monster effects cannot be activated.

Discarding and Special Summoning the discard with Lumina, Lightsworn Summoner
A common question is whether this effect can be used to discard a Level 4 or lower Lightsworn monster, and then Special Summon the same monster.

Lumina’s effect in question reads as follows:
Once per turn: You can discard 1 card, then target 1 Level 4 or lower “Lightsworn” monster in your Graveyard; Special Summon that target.

Now, if your Graveyard is empty (of Lightsworn monsters), you cannot attempt to activate the effect at all, even if you promise to discard a Lightsworn monster. The game doesn’t allow you to do it.

However, if you do have a Lightsworn monster in the Graveyard already, then you CAN do it. The activation is legal, so you can discard a Lightsworn monster, and since you ‘then’ pick a target, you can target the discarded monster at this point.

More Rulings
This section is for a variety of miscellaneous rulings to do with activation legality. By studying them, we can start to build an understanding of when we can and cannot activate things.

Here are some rulings about things you can’t do:

-You CANNOT activate Bottomless Trap Hole while Imperial Iron Wall is already face-up.
This is because you cannot attempt to banish while Imperial Iron Wall is out.

Note that the conjunction on BTH (‘and if you do’, in this case) is not relevant here. Conjunctions tell us how to resolve effects, and nothing about activation legality.

-You CANNOT activate Mind Crush if you don’t have a card in your hand, even if you ‘know’ you’re going to declare the right card.
This is because, if your opponent’s hand happened to not have the cards at resolution, you wouldn’t be able to attempt to discard anything.

-You CANNOT activate Dark Hole if the field is empty
This is because you wouldn’t have anything to attempt to destroy.

Now here are some rulings which tell us what we can do:

-You CAN activate the effects of monsters (and pay the cost to activate the effects) while their effects are being negated by Skill Drain or Effect Veiler.
This ruling is telling us that even though you know their effects will be negated at resolution, you can still attempt to activate their effects (this was mentioned in the last article).

-You CAN activate the effect of Divine Wrath to negate the effect of a monster in the Graveyard.
This ruling is telling us that even though you cannot destroy cards in the Graveyard, you can still attempt to do it.

-You CAN activate Bottomless Trap Hole on Beelze, King of the Diabolic Dragons.
This ruling is telling us that even though a card cannot be destroyed, you can still attempt to destroy it.

-You CAN activate Bottomless Trap Hole on Apoqliphort Towers.
Similar to the above ruling, this one is telling us that even though a card is unaffected by Trap effects, you can still attempt to use Traps on it.

-You CAN activate Foolish Burial to while Macro Cosmos is face-up.
This ruling is telling us that while all cards are being banished instead of being sent to the Graveyard, you can still attempt to send cards to the Graveyard as part of an effect. But recall from the principle of costs that you cannot try to do so to pay a cost.



There is more to move legality that we’re not going to go into here, and it can get quite hairy if you venture past the cases we’ve covered. For more complicated cases, it’s best to consult an article or check the rulings case by case.