what might the leaders of the committee of public safety have said to justify this law?

The leaders of the Committee of Public Safety would likely have justified a harsh revolutionary law (for example, something like the Law of Suspects or the Law of 22 Prairial during the Reign of Terror) by arguing that extreme emergency demanded extreme measures.

Core justification they might give

They would probably say something like:

• France is surrounded by foreign enemies and threatened by traitors within, so survival of the Republic comes before individual rights.

• Any delay in punishing “enemies of the people” risks the return of tyranny and the destruction of liberty.

• Harsh laws are temporary “weapons” needed to defeat conspiracy and win the Revolution, after which normal justice can return.

How they would frame it politically

Leaders such as Robespierre and Saint-Just tended to present such laws as:

• An expression of the general will : they would claim the law simply gives legal force to the people’s demand to be protected from aristocrats, priests, and counter‑revolutionaries.

• A necessary centralization of power: concentrating authority in the Committee and the Revolutionary Tribunal would be portrayed as essential for quick, decisive action in wartime.

Moral and ideological defense

To justify the severity (often death as the main penalty), they might argue:

• Virtue and terror go together: terror is “justice, prompt, severe, inflexible” in the service of virtue and the protection of innocent citizens.

• Better to sacrifice a few guilty (and even risk some innocents) than allow the entire Revolution, and the rights of millions, to be destroyed by its enemies.

What this might sound like in paraphrase

In paraphrased form, their justification could sound like:

“The Republic is besieged by kings abroad and traitors at home; if we are gentle to conspirators, we are cruel to the people.
This law arms justice against the enemies of liberty and protects the honest citizen, who has nothing to fear if he is truly a friend of the Revolution.”

TL;DR: They would justify the law as a temporary but necessary weapon to defend the Revolution and the people from internal and external enemies, placing collective security and revolutionary virtue above individual legal protections.

Information gathered from public forums or data available on the internet and portrayed here.