Can't amnesty players you trade for.
But, looks like he's only got a 10-17 mil guaranteed clause in his contract for next year.
That means it would be stupid for Washington to give up assets to rid themselves of Lewis for Jefferson, who gets 15 mil next year.
I proposed Lewis and Nick Young for Hayward and Jefferson in my "troll thread" partially for this reason. That trade is weighted in favor of Washington, but we'd clear the logjam, set for a rebuild, and have Nick Young. Young is leading the Wizards in scoring on almost 40% from 3, but he can't shoot much else with any efficiency.
https://jazzfanz.com/showthread.php?8422-Should-Hayward-be-benched&highlight=rashard