In a four person game of Quoridor, can a player be forced to pass a turn?
I would call this game a draw because there are no legal moves available to Yellow. Choosing how to resolve this on the spot would be unfair.



However, it is possible to come to an agreement to a solution before the game starts.

In a two-player game, this problem is addressed by allowing one to jump over an opponent.

Valid moves for "A"
╬═════╬═════╬═════╬═════╬
║     ║  ◎  ║  ◎  ║     ║
╬═════╬══╪══╬══╪══╬═════╬
║  ◎ ─╫─ A ─╫─ B ─╫─ ◎  ║
╬═════╬══╪══╬══╪══╬═════╬
║     ║  ◎  ║  ◎  ║     ║
╬═════╬═════╬═════╬═════╬


If I wanted to create a house rule to address this problem in four-player games, I'd simply extend the jumping rules.

Valid moves for "A"
╬═════╬═════╬═════╬═════╬═════╬
║     ║  ◎  ║  ◎  ║     ║     ║
╬═════╬══╪══╬══╪══╬═════╬═════╬
║  ◎ ─╫─ A ─╫─ B ─╫─ ◎  ║     ║
╬═════╬══╪══╬══╪══╬══╪══╬═════╬
║     ║  ◎ ─╫─ C ─╫─ D ─╫─ ◎  ║
╬═════╬═════╬══╪══╬══╪══╬═════╬
║     ║     ║  ◎  ║  ◎  ║     ║
╬═════╬═════╬═════╬═════╬═════╬


These movement options would be allowed at all times, not only when no other options are available.