Can I use Ride the Wind to move a unit I play to a battlefield if the opponent has Vex, Apathetic at the other battlefield?

Ruling: No, you cannot use Ride the Wind to move a unit you just played if your opponent has Vex, Apathetic at another battlefield. Ride the Wind is an [Action] spell and cannot be played in response to Vex's triggered ability since the chain is active (Closed State). Vex's ability will resolve, stunning your unit and preventing you from moving it that turn.

Sequence:

• You play a unit
• Vex, Apathetic's ability triggers and goes on the chain
• The chain is now active (Closed State), preventing [Action] spells from being played
• Vex's ability resolves: your unit is stunned and you cannot move it this turn

Nuances:

• The movement restriction specifically applies to "They" (the player who played the unit), so another player (such as a teammate in multiplayer) could still move that unit using their own spells or abilities
• Vex, Apathetic does not target; it programmatically selects the unit that was played