Would I be able to discard cards from my hand for the effect of Guzma & Hala when my opponent has Shiftry's "Shifty Substitution" Ability in effect?
No, all you can do is draw 3 cards.
Shifty SubstitutionGuzma & Hala
Shiftry
- Type
- POKEMON
- HP
- 150
- Energy Type
- Stage
- STAGE2
- Retreat Cost
- Weakness
x2- Regulation Mark
- D
- Rarity
- RARE
- Illustrator
- Uta
- Set
- Vivid Voltage (VIV)
- Number
- 12/185
Abilities
Shifty Substitution
As long as this Pokémon is in the Active Spot, each Supporter card in your opponent’s hand has the effect "Draw 3 cards." (This happens instead of the card’s usual effect.)
Attacks
Fan TornadoYou may have your opponent switch their Active Pokémon with 1 of their Benched Pokémon.
A Pokémon that was feared as a forest guardian. It can read the foe’s mind and take preemptive action.
Rulings (4)
If I play Lysandre 
when my opponent has Shiftry's "Shifty Substitution" Ability in effect, does Lysandre go to the Lost Zone or not after it has been played?
Shifty Substitution does not affect the Prism Star rule, so Lysandre would go to the Lost Zone.
Shifty SubstitutionLysandre {*}
If I play Nessa on my turn while my opponent has “Shifty Substitution” in effect, do I still get to Paralyze the opponent’s Active Pokemon if I use Drednaw’s “Vise Wave” attack?
Yes, because even though Shifty Substitution replaces Nessa’s usual effect the Supporter card still has the same name, so Vise Wave will still paralyze your opponent.
Vise WaveShifty Substitution
If I use Shiftry's "Fan Tornado" attack and my opponent has an Active Pokemon that used its "Swim Freely" attack on their last turn, can I still choose to have them switch their Active Pokemon with a benched Pokemon if they flipped heads for "Swim Freely"
No, the effect of Fan Tornado is targeting the Active Pokemon (not the Benched Pokemon), and therefore is prevented due to the effect of Swim Freely.
Fan TornadoSwim Freely