Sir William Anson remarks that "The Privileges of Parliament, like the Prerogative of the Crown, are rights conferred by Law, and as such their limits are ascertainable and determinable, like the limits of other rights, by the Courts of Law."[245:1] This principle has not always been accepted by the House, which has on several occasions come into collision with the courts; but the latter have always maintained, and maintained successfully, that when a question involving a privilege of the House comes before them for decision, it is their duty to ascertain whether the privilege exists or not, and to determine its effect upon the case before them. They have further maintained that they must decide the question for themselves, and that a claim to the privilege on the part of the House is not conclusive. In one respect the authority of the courts is incomplete; for the House has a right to order a man committed to prison for contempt, and the question what constitutes a contempt is so far within the discretion of the House that the court will not order the prisoner set at liberty on _habeas corpus_ where the return to the writ simply states that he is committed for contempt by order of the House. Referring to this subject, Professor Dicey says: "The powers exercised by the Houses, and especially in practice by the House of Commons, make a near approach to an authority above that of the ordinary law of the land."[245:2] Such a power, however, is exceedingly unlikely to be used in any dissension with the courts to-day; and if it were used, the courts would be almost certain to win, because the commitment by the House terminates with the session. [Sidenote: Summons and Dissolution.] There remain to be considered only the methods of calling Parliament together, and of putting an end to its labours. Parliament can be summoned and dissolved, and its sessions can be opened and closed by the Crown alone, the only legal restraint upon the arbitrary power of the sovereign in the matter being the Act of William and Mary, which provides that a new Parliament shall be summoned within three years after a dissolution.[245:3] This statute is now, of course, unnecessary; and, in fact, the same proclamation which dissolves one Parliament always announces the issue of writs for the election of another. If Parliament is not dissolved by the Crown, its term expires at the end of the seven years prescribed by the Septennial Act of 1716; but, as a matter of fact, Parliament never dies a natural death, and if its life is not cut off earlier, a dissolution takes place shortly before the end of the seven years. Until 1867 the death of a sovereign always wrought a dissolution of Parliament; but this rule, which depended more on ancient theory than on modern convenience, was abolished by the Reform Act of that year. [Sidenote: Prorogation and Adjournment.] [Sidenote: Effect on Unfinished Business.]