Rule of Law
Enchantment
Each player can't cast more than one spell each turn.
The law is meant to ensure that people kill each other with only the utmost fairness.
Illustrated by
Core Set 2020#35UncommonEnglishLegality
Rulings
Jul 12, 2019
Rule of Law looks at the entire turn to see if a player has cast a spell, even if Rule of Law wasn’t on the battlefield when that spell was cast. Notably, you can’t cast Rule of Law and then cast another spell during the same turn.
Jul 12, 2019
If you cast a spell that was countered, you can’t cast another spell during the same turn.