Whenever a player casts a spell from their hand, Knowledge Pool triggers, exiling that spell.
Because Rule of Law prevents players from casting more than one spell each turn, players cannot cast the spell permitted by Knowledge Pool, or any other spell that turn

Exile all spells cast from a player's hand

Players can only cast one spell per turn

Knowledge Pool

Rule of Law

Any time a player would cast a spell from their hand it gets exiled from possibility storm.
Rule of Law prevents them from casting the other card from possiblity storm resulting in a lock.

Combos with "Rule of Law"