Even steven

Restitution.  That which makes up for the wrong done.  But not really.  Legally speaking, it just means that any benefit the wrongdoer has gained must be disgorged.  Unjust enrichment would be...unjust.

It's like the big brother tricking little brother into handing over his allowance-big brother must give it back, even in the face of an agreement between the brothers.  Why?  Because it would be unfair to do otherwise.

Sometimes the court is a lot like a parent.