Royal baby law comes into effect across the Commonwealth

Good news, current and future royal princesses: as of today, your spot in the line of succession will no longer be bumped back by the birth of a baby brother.

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You're also free to marry a Roman Catholic without forfeiting your right to take the Throne, but you still can't convert to Catholicism yourself and expect to keep your status as an eligible heir.

The new succession rules came into effect across the Commonwealth on Thursday after Australia became the final realm to sign on.

"I am delighted today that Canada is joining the Realms of the United Kingdom, Australia, New Zealand, Barbados, St. Kitts and Nevis and St. Vincent and the Grenadines in bringing legislation into force that gives assent to changes to the rules governing the line of succession," Prime Minister Stephen Harper said in a written statement.

Canada's consent constitutionally controversial

"The changes, which will put an end to the practice of placing male children before their elder sisters in the line of succession and which will remove legal provisions that heirs marrying Roman Catholics would be ineligible to succeed to the Throne, are very much in keeping with the values that Canadians cherish."

The move to update the ancient edict laying out who can and cannot succeed to the Throne was sparked by the news that Prince William and Kate were expecting their first child, the sex of which was unknown at the time.

Under the previous rules, had George turned out to be a Georgina, she could theoretically have lost her right to rule to a younger male sibling. 

While Canada formally assented to the change with the passage of its own bill in 2013, the question of whether the federal government had the power to do so without consulting the provinces is still before the courts.

The federal government moved unilaterally, with then-heritage minister James Moore telling reporters it didn't need to consult because no province proactively expressed its disapproval with changing the rules. But a few spoke up after the fact about a process they didn't appreciate.

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The law is being challenged in Quebec Superior Court by a group of legal scholars and constitutional experts. That case is expected to be heard later this year — and the outcome of that case could have repercussions far beyond Canada's borders, as the assent of all Commonwealth Realms was required for the new rules to be adopted.

University of Ottawa professor Philippe Lagassé predicts that, should the court concur with the Quebec scholars challenging the law, and conclude that the assent had no effect on succession in Canada, the case will be appealed to the Supreme Court.

"If the [Supreme Court] also finds that the assent had no effect, I suspect the U.K. will decide to keep the changes and let us come into line over time," he told CBC News.

"Given the international stakes, there will be enormous pressure on the courts to find that assenting is sufficient," Lagassé says.

But if the court does ultimately side with the government, "they'll need to figure out a way to deal with what would happen to the office of the Queen in Canada if the U.K. abandoned the monarchy," he notes.