(_lex data_), which as late as 71 B.C. is still an utterance of the people (_lex rogata_).[1203] We shall see, in dealing with the Senate, that, even in this matter of granting treaties or charters to separate states, senatorial authority encroached on that of the people. (ii.) We have already seen how in theory the popular power of election was a modification of a principle of nomination;[1204] after its recognition the principles regulating it were practically those of legislation, the magistrate questioning and the people commanding. The representation of the dual community is here rather more marked than in the case of legislation; for while a _plebiscitum_ is often spoken of as a _lex_, no one credits the tribune with the position of a _magistratus populi_, and however wide his powers may have become, he always remains in theory the head of the plebeian community. The preliminaries to election necessary to the candidate for office have already been considered,[1205] and the further process of election will be dealt with when we describe the procedure of the _comitia_ as a whole. (iii.) The origin of the jurisdiction of the people is, as we have seen, obscure; but it is probable that it did not spring wholly from the _provocatio_,[1206] and even in cases where it did, the appeal tended to become extinct, from the fact that a magistrate who recognised the restrictions imposed on his _imperium_ by law would not pronounce a sentence, but would bring the case immediately before the people. A trial before the people (_judicium populi_) took place when a magistrate recognised the limitations on his power; the _provocatio_—an extremely rare occurrence in the later Republic—was required to start the same procedure when the magistrate refused to recognise these limitations. The judicial competence of the different magistrates and _comitia_ was determined partly by law, partly by custom. Two fundamental principles were recognised:— (1) That capital cases should be reserved for the centuries. To this there is the exception furnished by the special capital jurisdiction of the Plebs.[1207] (2) That a case initiated by a magistrate could be tried only in that assembly which the magistrate was competent to approach. To this principle there were two exceptions: first, the consular delegates—the quaestors and the _duumviri perduellionis_—although possessing no _jus agendi cum populo_, yet guided the assemblies in which an appeal from their decision was made;[1208] and secondly, the tribune, when conducting a capital prosecution before the _comitia centuriata_, approached, and perhaps had the presidency of, this body.[1209] But, as a rule, the official character of the magistrate who conducts the prosecution, and the nature of the penalty which he proposes, are signs of what assembly passes its final judgment on the case.