A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 2 April 2014
1) Is legal to announce this ability in standard 1vs1 game (questionable Multiplayer keyword)? 2) In 3 players game (player A, B and C), A uses this item and targets player B then A attacks B. Does sentence 'and may not assign units elsewhere' mean that player B can't assign any Personalities to defend his provinces?
Multiplayer Open [bow]: Target a player. Until your next turn begins, each of you must invite the other to ally (if legal), and during Maneuvers, the invited one must assign a unit to an army where the other has a unit, and may not assign units elsewhere.
A player, 2 April 2014
1) Is legal to announce this ability in standard 1vs1 game (questionable Multiplayer keyword)?
Yu may announce it, but it will fail to produce any effects because players can't use the multiplayer rules in 1 vs 1 games.
2) In 3 players game (player A, B and C), A uses this item and targets player B then A attacks B. Does sentence 'and may not assign units elsewhere' mean that player B can't assign any Personalities to defend his provinces?
If A uses this item and targets B, he may not attack B because he must invite B to ally because of the item itself. declaring an attack on B will cause the effects to fail. As they can't invite the Enemy Leader as her ally, everything else fails to occur (since the effects refer to the "invited one"), and B may assign freely.