Meddling Mage

From the Oracle rulings:

Quote :

5/1/2009 Once Meddling Mage leaves the battlefield, the named card can be cast again.

Meddling Mage

This is known as a static ability.

Quote :

604. Handling Static Abilities

604.1. Static abilities do something all the time rather than being activated or triggered. They are
written as statements, and they’re simply true.

604.2. Static abilities create continuous effects, some of which are prevention effects or replacement
effects. These effects are active as long as the permanent with the ability remains on the battlefield
and has the ability, or as long as the object with the ability remains in the appropriate zone, as
described in rule 112.6.

The rules also apply to Iona, Shiled of Emeria. Once she leaves play, her ability is no longer in effect. Something interesting from the oracle rulings though:

Quote :

10/1/2009 Once the color is chosen, it's too late for opponents to respond by casting spells of that color. Iona is not yet in the battlefield at the time the color is chosen, so, for example, there's no way for an opponent to destroy it by casting Doom Blade if the chosen color is black.

hahah lovely, thanks for pointing that out sam. I honestly had no clue about my mages. Otherwise they'd be so broken.

So if you choose Cancel with Meddling Mage, your opponent can't use Cancel on her?

You can cancel Meddling Mage while she is still on the stack, before she resolves, even if Cancel is the named card. The reason you can't Doom Blade Iona is because she is already resolved by the time you can target her. You can't Doom Blade something while it's still on the stack, the target needs to be already in play.

Ah yes... I forgot that Cancels have a stupid priority rule to them... but the second rule here suggests that it would work unless the timing is different:

Meddling Mage rulings taken from here:

2/1/2006 If you somehow manage to cast this while other spells are on the stack, those spells won't be countered.
5/1/2009 No one can cast spells or activate abilities between the time a card is named and the time that Meddling Mage's ability starts to work.
5/1/2009 Spells with the chosen name that somehow happen to already be on the stack when Meddling Mage enters the battlefield are not affected by Meddling Mage's ability.
5/1/2009 Although the named card can't be cast, it can still be put onto the battlefield by a spell or ability (if it's a permanent card).
5/1/2009 If you want to name a split card, you must name both halves of it (for example, "Boom // Bust"). Neither side of that split card (Boom or Bust) can be cast.
5/1/2009 If a card with morph is named, that card may still be cast face down. Face-down cards have no names.
5/1/2009 Some cards (such as Isochron Scepter, for example) let you cast a copy of a card. A copy of a card isn't actually a card, so Meddling Mage can't stop this.
5/1/2009 Once Meddling Mage leaves the battlefield, the named card can be cast again.

Again I'm probably wrong but it's fun to explore this.

cancel prevents her from ever entering the battlefield thus her ability is never triggered so it's illrelevent