(3) A check upon such exactions was sought, not in any action by the court baron, but in the mesne lord’s need for a royal licence. The necessity for this may at first have been a practical, rather than a legal, one; for executive power lay with the officers of the Crown alone, and the sheriff gave his services only at the king’s command.[520] The Crown thus exercised what was virtually a power of veto over all aids taken by mesne lords. Such a right, conscientiously used, would have placed an effectual restraint on their rapacity. John, however, employed it solely for his own advantage, selling writs to every needy lord who proposed to enrich himself (and, incidentally, the Crown also) at his tenants’ expense. ----- Footnote 520: In theory, in Henry II.’s reign at least, a royal writ was _not_ required in the normal case. See _Dialogus_, II. viii., and the editors’ comment (p. 191): “Normally the levying of money under any pretext from a land-owner gave him a right to make a similar levy on his under-tenants.” As regards _scutage_, a distinction was recognized. The lord who actually paid scutage might collect it from his sub-tenants without a licence; but, if he served in person, he could recover none of his expenses except by royal writ. See _Ibid._, and cf. Madox, I. 675. It is necessary, however, to avoid confusion between two types of writ, (_a_) that which merely authorized contributions, _e.g._, _de scutagio habendo_; (_b_) that which commanded the sheriff to give his active help. ----- Magna Carta forbade the two tyrants thus to combine against the sub-tenants, enunciating a hard-and-fast rule which, if duly observed, would have struck at the root of the grievance. The whole subject of aids was removed from the region of royal caprice into the region of settled law. No writ could be lawfully issued except on the three well-known occasions. II. _The Influence of Magna Carta upon later Practice._ This chapter, along with chapters 12 and 14, was discarded by Henry III.; and little difference, if any, can be traced between the practices that prevailed before and after 1215. Only in one particular were the requirements of John’s Magna Carta observed, namely, as regards the need for obtaining a royal licence. Mesne lords after this date, whatever may have been their reason, invariably asked the Crown’s help to collect their aids. They could not legally distrain their freeholders, except through the sheriff, and this was, in part at least, a result of Magna Carta.[521] ----- Footnote 521: Cf. Pollock and Maitland, I. 331: “The clause expunged from the Charter seems practically to have fixed the law.” -----