Am I right in thinking that, until the civil unrest around the careers of the Gracchi, there was no such thing?

One of the major danger signals in the late Republic, IMHO, was the resort fo the Senatus Consultum Ultimum (I know, it has a much longer name which I can never remember) in times of crisis. If I understand Cicero's argument, he felt that, having the Senate pass the SCU, meant that any and all measures taken by the Consuls to defend the Republic were completely covered; murder, torture, rape, execution without trial. I always think of an Old West with Martial Law being in force.

I think part of the problem - where Caesar thought that Cicero was wrong and Cicero argued he wasn't - is that it was a relatively new device and had not been used all THAT often by the time of Catiline's conspiracy (it seems in the late '50's it was used much more and certainly, by the time of the Civil War). However it had been used between the Gracchi and the Catiline Conspiracy, it had never been pushed nearly so far as execution without trial, so there was no precedent for the act, even though there was for the broad principles of the SCU.

It has always seemed to me that having to resort to the SCU to put down street violence that could not be controlled by the Magistrates or the laws, was a major fire bell in the night about the declining Republic.