If Klefki with the "Wonder Lock" Ability is attached to a Pokemon as a Tool card, what happens if "Silent Lab" stadium comes into play? Does "Wonder Lock" shut off and Klefki get discarded, or does it remain attached to the Pokemon?
Once Klefki is attached as a Pokemon Tool card it retains its effect even when its Ability has been disabled. Once it's attached, it is essentially treated as a Tool with that text, so shutting off its Ability doesn't matter at that point. However, if something such as Lysandre Labs is in effect, Klefki won't be discarded at the end of your opponent's turn.
Source: TPCi Rules Team (2019-01-03)
When I have seven cards in my hand, can I discard only one with "Sightseer"?
No, you cannot. You must discard until your hand has 4 or fewer cards when using Sightseer.
Source: TPCi Rules Team (2018-12-06)
If I use Sylveon's "Wink Wink" attack to have my opponent discard Ilima, can I use Victini's "Victory Star" Ability to force my opponent to re-flip their coins?
Yes, you can. If your opponent flips a coin as part of your Pokemon's attack, you can use "Victory Star" to force them to re-flip those coins; but keep in mind you will have to re-flip your coins for Ilima too.
Source: TPCi Rules Team (2018-11-15)
If my opponent used Gardevoir EX's "Shining Wind" attack to gain "no Weakness" and I play Pokemon Ranger when it is my turn, does their Gardevoir EX have a Weakness again?
Yes. The ruling about effects on Weakness and Resistance not being ignored has to do with damage calculations [see "General Gameplay -> Weakness and Resistance" section for reference], not about whether a Pokemon HAS Weakness or Resistance. Pokemon Ranger removes attack effects, including this one; so yes, Gardevoir EX would have Weakness again after using Pokemon Ranger.
Source: TPCi Rules Team (2018-11-15)
Is there any way to clear the effect of Lusamine {*}?
No, however any attacks that ignore effects on the Defending Pokemon would get through its effect.
Source: Lost Thunder FAQ (2018-10-20), TPCi Rules Team (2018-11-01)
Can I play Kahili if there's only one card left in my deck?
If you can draw at least 1 card from your deck, you can use Kahili and do the coin flip part. But if you can't draw any cards, you can't use it.
Source: Lost Thunder FAQ (2018-10-20), TPCi Rules Team (2018-11-01)
Can I play Fiery Flint if I only have 1 card in my hand to discard?
No, you must be able to discard 2 cards in order to use Fiery Flint.
Source: TPCi Rules Team (2018-09-27)
Does using Beast Ball count as "taking a prize" for the purpose of calculating damage for Stakataka GX's "Assembly GX" attack?
No, it does not. You are switching cards, not taking a prize.
Source: TPCi Rules Team (2018-08-16)
Sky Pillar says, "Prevent all effects of the opponent's attacks, including damage, done to Benched Pokemon (both yours and your opponent's)". So does this mean if I use an attack like Zapdos' "Raging Thunder" that I do not apply the bench damage to my own Pokemon?
No, only bench damage done from an opponent's attacks is prevented by Sky Pillar. If your attack does damage to your own Benched Pokemon it is not prevented.
Source: TPCi Rules Team (2018-08-09)