[soulofmischief]

Relativity was derived as a direct consequence of imposing an invariant speed of causality to the Lorentz transformations, therefore it cannot tautologically be used as justification for an invariant speed of causality.

[cjfd]

"Imposing an invariant speed of causality to the Lorentz transformations" does not sound quite right. I think it is more like assuming that the Lorentz transformations are the true symmetry of mechanics. If one wants to keep that causal, there cannot be information moving faster than the speed of light because there is a reference frame where said information would be moving backwards in time.