New constitution or guardrails script is a governance action that adopts a new version of the Cardano Constitution or updates the guardrails script. The constitution is the document all governance actions are checked against; the guardrails script is its enforceable on-chain counterpart, a script that constrains which protocol parameters may change and within what bounds.
The action is voted on by DReps and the Constitutional Committee. Because the constitution defines the rules the committee itself enforces, changing it is one of the most consequential actions in the system. Constitution and guardrails topics are discussed in the Constitution and Guardrails category.