What happens if a unit is moved to an opponent's base (e.g., via Charm or other effects)?

Ruling: Units cannot be moved to their opponent's base - this is an illegal move that cannot happen. If an effect would do this, it either must describe how to resolve the situation or the effect would fizzle.

Nuances:

• This is different from Gears on battlefields: battlefields are not illegal locations for Gears, but cleanup rules send them to base
• If a future Golden Rule effect would permit a unit in an opponent's base, that effect would need to describe how to resolve the situation and its impact on other rules
• No automatic recall or destruction occurs because the rules don't cover this scenario - it simply cannot happen unless explicitly allowed and explained by a card effect