At its heart, the three changes that comprise the bill to change the Royal line of succession are about removing discrimination and adding more freedom to a centuries-old system.

The bill ends the preference for males over females, removes a ban on marrying Roman Catholics, and abolishes the need for certain, more distant members of the royal family to have the sitting monarch approve their marriages.

But does talk of rights and freedoms even make sense when it comes to the Royal Family?

Technically, the monarch is not a citizen or a legal subject of the country over which he or she reigns, so laws and legal rights don't really apply to him or her. The person wearing the crown stands apart from his or her subjects.

A Canadian monarch isn't likely to mount a Charter of Rights challenge demanding the right to freedom of religion, for example.

But the reforms soon up for discussion in Canada's Parliament would be an important symbol of an institution based on bloodlines at least trying to more closely resemble the more merit-based democracy over which it presides.

"The minute you start talking about removing discrimination from the crown — which is inherently discriminatory — it starts becoming weird," admits Philippe Lagassé from the University of Ottawa.

Other parts of the system need revisiting?

Indeed, as British constitutional expert Robert Morris told the committee of British MPs studying the rules of succession last November, it is hard "to infuse logic into a system that isn't logical."

So these changes could open what Northern Ireland's Ian Paisley last week called "a royal Pandora's box." By that, the former leader of the Democratic Unionist party meant that once the first changes come up for debate, other questions will likely emerge about the wider role and entitlements of the Royal Family in 21st-century democracies.

In the case of the U.K., the system also includes inherited titles and property, including the hereditary peerages in the House of Lords, Britain's upper house. 

Prince Charles, the first in line to the throne, also has reportedly raised private concerns that the British legislation may have unintended consequences for other titles and entitlements handed down through the male line. (He is also said to be concerned about the change to allow a potential heir to the throne to marry a Roman Catholic.)

The passing on of titles and land across the British aristocracy would not become gender-neutral under the limited scope of this bill, so some feel the reforms don't go far enough.

Removing gender discrimination across the system could help bring more women into the upper house of the British Parliament too. The roughly 10 per cent of seats still allocated to "hereditary peers" in the House of Lords remain male-dominated.

Cue the republicans?

Both inside and outside the U.K., if the public debate doesn't stop at the specific, old-fashioned rules this bill addresses, republicans may see an opening to reconsider the entire system.

Canada's republican movement is not as strong as it is in Australia, but it does exist. While this legislation is intended to be a simple, quick process of making limited reforms, some may want a wider debate.

The Parti Québécois government in Quebec so far has been officially mute on how it feels about the reforms. But in the House of Commons, sovereigntist Bloc Québécois MPs seem unlikely to agree to anything that renews or modernizes the institution of the monarchy, so unanimous consent for the Canadian bill seems unlikely.

That would mean it will likely have to pass through the House of Commons in the usual, stage-by-stage fashion.

Would other republican-leaning MPs also give voice to concerns? What would potential parliamentary committee hearings draw out?

And will the Harper government be forced to set time limits on the bill to keep its commitment to the Commonwealth? British Prime Minsiter David Cameron fast-tracked his government's legislation.

The prime minister's office has said from the start it wants this bill passed "quickly."

Perhaps otherwise, legislation intended to breathe new life into a centuries-old institution may end up giving birth to other changes.