Code of Constraint

• WWizards of the Coast2019-01-25
  Official Ruling
  If the target creature is an illegal target by the time Code of Constraint tries to resolve, the spell doesn't resolve. You don't draw a card.
• WWizards of the Coast2019-01-25
  Official Ruling
  Code of Constraint can target a creature that's already tapped. If you cast it during your main phase, that creature won't untap during its controller's next untap step.
• WWizards of the Coast2024-01-12
  Official Ruling
  Addendum abilities of instant spells apply while the spell is resolving, not immediately after casting it. If the spell is countered, you don't get the addendum bonus.
• WWizards of the Coast2024-01-12
  Official Ruling
  If an effect copies a spell with an addendum ability while it's on the stack, the copy wasn't cast at all, so you won't get the addendum bonus.

Rulings via Scryfall