Power of the Charisian Throne
All right -- you guys asked for it, so don't blame ME for the length of this! And BTW, the reason I'm using all caps for emphasis rather than ital isn't to shout at you but because I composed this off-forum and didn't want to hunt through it to find and reformat each emphasized word.
We haven't discussed how Constitutional law works in Charis because it hasn't really been important to the story. That doesn't mean it hasn't been important to what's happening (or to the characters in their off-screen lives), but that the actual mechanisms haven't been crucial to the results the reader has had to see.
Unlike most medieval Terran monarchies, Charis has a written constitution which was promulgated by the House of Ahrmahk after Saint Zherneau's journal had revealed the truth about the “Archangels.” It was intended to provide a basis which might later be transitioned into a constitutional monarchy (in our present sense of the term) while conserving the power of the Crown at the moment, and so it favors the Crown rather heavily over Parliament.
Essentially, the Crown can rule by decree, and its decrees need not be approved by Parliament to take effect. However, Parliament can by a majority vote of both houses repeal and negate any royal decree within a half-year of its promulgation; after that, it requires a two-thirds super-majority of both houses to repeal a decree. This means (in effect) that Parliament has a collective veto power over the Crown, although the process is complicated enough that it's not real likely to happen (especially since a smart monarch will withdraw or modify a decree which is generating that much resistance before Parliament gets into the habit of overruling him).
The Crown also controls fiscal policy and establishes tax law and Parliament cannot repeal Crown policy (except by a majority vote of both houses, as described above), but Parliament does have the power to ammend existing tax law. Because the Crown can (and normally does) rule by decree which (in effect) simply has to be approved by a majority of one house to remain law, the Council, as the Crown's advisor and executor, is of special importance under the Charisian Constitution. The House of Commons' biggest stick is that it has the responsibility of approving (and the right to recall) all members of the Council. The Crown determines which councilor holds which “portfolio” (including the First Councilor's position), but the Commons (by majority vote) can control who sits on the Council. The House of Lords doesn't get to confirm members of the council, but it can move to remove a councilor. The process is sort of a mirror image of the US Constitution's impeachment process (except that it can be exercised for any reason, not for specifically enumerated offenses against the Constitution) in that a simple majority of the Lords can call for a councilor's removal but that the actual removal must be confirmed by a two-thirds majority of the Commons.
The House of Lords' biggest stick is that it serves as the kingdom's supreme court in constitutional matters (the King's Bench is the supreme court in criminal matters, which has the potential to lead to a clash of authorities), which means that the Lords are the final determiners of what the Constitution actually says. In addition, the Lords must confirm the succession to the throne. The Constitution doesn't specifically address the question of inheritance, but Charisian tradition enshrines male primogeniture. The Constitution does, however, provide that the House of Lords can refuse to accept the “proper” heir and move further down the line of succession. The Lords are required to approve an heir as soon as a new monarch assumes the throne, however. This means that the succession is always secured, by act of Parliament, without room for a disputed succession in the event that a monarch dies childless. The Lords can alter the succession at any time, but that requires a two-thirds vote rather than a simple majority, and they'd probably better be sure they really want to get into a pissing contest with the Crown if they decide to do so without a damned good reason.
The Crown determines foreign policy and negotiates treaties and alliances, but any formal treaty must be approved by both houses of Parliament. (This means that Cayleb's proposal of marriage required parliamentary consent. As one may have noticed from reading the books, however, Cayleb didn't say a word to Parliament until he announced what was effectively a fait accompli. That reflected not simply the absolute necessity of keeping the negotiations coompletely secret until they were concluded but also the fact that he knew damned well Parliament would accept it, in no small part because he had discussed it intensively with the critical members of his council (who tend to keep in touch with little things like the mood of Parliament). In addition, of course, there was the minor fact that it was a matter of national survival and that no one in his right mind wanted to piss Cayleb off at that point in his reign.)
The Crown also makes and determines military policy (which includes procurement fiscal policy covering --- very specifically --- shipbuilding). The monarch is also commander-in-chief, and the military's oaths are sworn to the Crown not the Constitution. (A minor point, after all which the Crown made darned sure was enshrined under the Constitution.
) The Crown does not require a formal declaration of war from Parliament to commit the kingdom's military forces, but Parliament can use its power to amend tax policy to starve the Crown of funds for military operations of which it does not approve. This is a time-consuming process, however, and leaves Parliament without effective control of the kingdom's military operations. Nor has it ever actually been employed in Charisian history.
Parliament does have the power to initiate legislation. All bills must originate in the House of Commons but are amendable (and must be approved) by both houses. However, no act of Parliament can become law without the Crown's assent, and Parliament does not have the power to override the Crown. (It would always be theoretically possible for Parliament and the Crown to get into the equivalent of a series of nuclear exchanges with both sides effectively vetoing the other side --- in Parliament's case by repealing existing Crown decrees and “amending” tax laws out of existence before allowing them to pass --- until one side or the other gives up. This has not happened in Charisian history to date, however.)
There is a formal procedure for amending the Constitution. Amendments can be proposed by Parliament (simple majority of both houses) or by the Crown. To become law, an amendment must be approved by a two-thirds majority of both houses and the Crown. An amendment can become law over the Crown's objections only if it can be approved by a two-thirds majority of both houses in successive parliamentary sessions. The sessions in question need not be immediately successive to one another; that is, there is no limit on how much time can pass between the two parliaments which ultimately approve the amendment.
As far as the succession in Old Charis is concerned, the Lords had confirmed the succession before Haarahld's death as : Cayleb, Zhan, Zhanayt. When Cayleb became king, the succession became Zhan, Zhanayt, Rayjhis Ahrmak (minor Duke of Tirian). The big problem with the succession at this point (of course) was that all the immediate heirs were minors, but Zhanayt wasn't enough older than Zhan (in Parliament's view) to alter the succession, and Parliament was not prepared to move beyond Cayleb's immediate family to name a more distant adult relative as his heir although it could in theory have done so. Cayleb and his council had named Gray Harbor as his regent in the case of his death in order to provide the greatest possible continuity in the case of a minor reign.
Under the Constitution, Parliament must meet yearly and must sit for a minimum of four months a year. There is no maximum length on a session of Parliament, and the Crown cannot dissolve it against its will until it has sat for its minimum of four months in a year. In other words, the monarch can't simply dismiss Parliament and rule by unchecked decree the way Charles I attempted to do in England and the French kings after Louis XIII did regularly up to the Revolution. Members of the House of Commons are elected for three year terms, not for the duration of a single Parliament, and elections are staggered, with one-third of the boroughs holding elections each year. The Crown is specifically prohibited under the Constitution from arresting or imprisoning any member of Parliament for any offense during sessions of the Parliament in which he serves. Even MPs or Lords who have been imprisoned for some other offense between sessions must be released to take their seats during the current session.
The Church, under the original Constitution, holds ultimate veto power over any purely political act in that the Church through the local archbishop and/or his intendant may rule any act is not in accord with God's law as revealed through the Archangels. (This is the case for any Safeholdian realm, not simply Charis.) The Church also holds ultimate authority over the confirmation of any title of nobility, since the succession cannot become legal without the Church's attestation. (This was the reason the Church had final authority in the disputed succession in Hanth.) It has historically been very rare for the Church to have to intervene that “crudely” in domestic political affairs because the Church is guaranteed a large percentage of the seats in the House of Lords in every Charisian kingdom and --- in most Charisian kingdoms --- the Lords dominate the Commons. (This was one reason the Church was prepared to whack Chisholm as soon as Charis was out of the way even before Sharley married Cayleb; Chisholm was giving the Commons too much power. The situation in Harchong, where a reactionary nobility is completely loyal to the Church, is the Temple's ideal political equation. This, of course, is another reason the Church is unhappy with the Republic, where the Lord Protectorship is elective and the legislative authority lies in the hands of an elective senate rather than an hereditary nobility which can be seduced/coopted into serving the Church's ends out of self interest.)
As part of the marriage contract with Sharleyan, Zhan (who had already been confirmed by Parliament as heir to Old Charis until Cayleb produced a child) was made their joint heir because Sharleyan had no siblings or children. Indeed, the succession question in Chisholm was a bit vague, and Sharleyan's need to produce an heir (or to do an Elizabeth I tap dance about who she might marry as a diplomatic weapon) was a major policy issue for her and her council. The agreement to make Zhan their joint heir satisfied existing Charisian law and clarified the succession for Chisholm (and, of course, the Empire as a whole), while the provision that either partner became joint heir to both thrones in the event one of them died (and the relative youth of both of them, with the promise that additional joint heirs could --- and would --- be produced) went a long way towards quashing any lingering temptation to depose Sharley among the Chisholmian peers. It also solved the problem of minor heirs in Charis, since it provided Sharleyan (an adult and obviously very competent monarch in her own riight) as Cayleb's heir if anything happened to him. When Crown Princess Alahna was born, she automatically became first in line to the imperial crown because of the specification of the marriage contract (she is the only “heir of their joint bodies” in existence), although Zhan remains next in line behind her. The Imperial Constitution, moreover, provides that the heir to the crown is the firstborn child, regardless of gender, since they could scarcely exclude female heirs with Sharleyan specifically named to succeed Cayleb if he should pre-decease her.
The Imperial Constitution differs from the Old Charisian constitution in several other minor particulars but follows it in general. The Chisholmian “constitution” was largely unwritten, with the power of the Crown waxing and waning (which was the problem Sharleyan's father had in recouping the Crown's power). Sharleyan, however, was a very strong monarch, which meant she and Green Mountain had near absolute power when Cayleb's proposal arrived (and explains the reason she was able to announce to her Parliament that they were going to do things her way). By signing onto the imperial Constitution, she has in effect accepted a de jure limitation of her powers, although in a de facto sense she and Cayleb remain very nearly absolute monarchs under the current conditions.
I'm not going to kill you off, because you raised good points.
First point: The process is that the Crown can veto an amendment even if passed by a 2/3 majority unless it is passed by a 2/3 majority twice in separate sessions of Parliament. That is, the Parliament cannot immediately hold a second vote to override the Crown; it must wait until a new session, following the election/reelection of at least 1/3 of the House of Commons before it can attempt the second 2/3 majority vote to override the Crown. In my opinion, that's actually a stiffer requirement than demanding a 3/4 majority in the same Parliament which already disagreed with the Crown.
Second Point: The Parliament of Old Charis cannot modify the imperial succession, and the crowns of Old Charis and Chisholm will be united in either Sharleyan or Cayleb (should one predecase the other) or in Princess Alahana or another of their children. Thereafter, those two kingdoms cease to exist as separate entities (so far as the succession goes) and the Imperial Parliament has the authority to modify the succession. There are some additional limitations on how easily the succession can be altered once set; that is the Imperial Parliament would find it even more difficult than the Parliament of Old Charis to remove someone from the succession once that succession has been approved. It's not flat out impossible, but doing it without the approval of the current monarch would be very, very hard, and the succession cannot be changed, under any circumstances, between the death of the current monarch and the coronation of his sucessor. That is, there is no legal inerregnum in which Parliament may tinker with the succession.
Hope this helps clarify.