unregistering action callbacks?

I register a character to an input (movement in this case)

Code (CSharp):

1. controls.CharacterControl.Movement.performed += ctx => player.Move(ctx.ReadValue<Vector2>());

and when wanting to switch to another controllable character, I unregister the original als follows

Code (CSharp):

1. controls.CharacterControl.Movement.performed -= ctx => player.Move(ctx.ReadValue<Vector2>());

Fairly sure I'm following instructions to the letter here, but the original character keeps responding to input and moving around (in other words; he did not unregister from the callback)... Am I missing something here?

 

Ok, I believe I found the answer here
https://answers.unity.com/questions/1767382/removing-event-from-new-input-system-not-working.html

Seems this way of doing things creates a new lambda function.
If will have to either pass context to player.Move() or create an intermediate function that takes the context and reads the Vector2() value and have that function call player. I can then register/unregister that intermediate function.