Each player can't cast more than one spell each turn.
Decree of Silence
Erayo, Soratami Ascendant // Erayo's Essence
More combos with Arcane Laboratory
When it leaves the battlefield, the effect ends and all players are able to cast spells unrestricted again.
When Arcane Laboratory enters the battlefield, it will look back over the turn to see if any spell was cast before it entered the battlefield. It will notice itself being cast.