Hi Jasper,
It's not either player's responsibility to point out that an ability is countered by game rules until that becomes relevant to the game state. Declaring Winding Constrictor as a blocker seems like an ideal time to do this. At Competitive REL, I would briefly explain to the players why this outcome has happened (last known information shows us Earthshaker Khenra has -2 power, certainly lower than Winding Constrictor's +2 power!) but otherwise leave them to get on with their game.
At Regular REL, this sequence of events is perfectly legal however it is not so sporting. Use your judgement if you would like to encourage Noah to point these things out in future (and keep in mind that Adalbert can't use this information completely usefully once they've declared attackers), depending on the atmosphere you would like to foster at your events, but don't issue any penalty or suggest that Noah might receive a penalty if they continue to play this way.
If Adalbert had solicited this information, then Noah would have to answer truthfully but Adalbert just went to attacks without asking. Patience is a virtue!
Edited Winter (July 31, 2017 05:49:35 AM)