The high court’s unanimous decision about the “citizenship seven” may have added a splash of drama to Friday afternoon, but it will probably not have a substantial impact upon on the current government beyond some minor changes in personnel. Four senators will be replaced by whoever followed them in winning the next greatest number of votes, which is unlikely to significantly change the composition of the Senate. Barnaby Joyce’s seat will go to a byelection, which he is fairly likely to win. Senators Matt Canavan and Nick Xenophon survived only because the court held that neither actually held foreign citizenship.

There are nonetheless some interesting anomalies that arise. In the Senate, the consequence of a joint Coalition ticket for New South Wales will mean that the National party’s Fiona Nash will most likely be replaced by a Liberal. This will upset the balance between the Coalition parties in the Senate and exclude a minister from parliament. It has been suggested that the likely Liberal winner in a recount, Hollie Hughes, might be pressured to resign her seat, giving rise to a casual vacancy that could be filled by Nash.

The constitution, however, does not work that way. It requires the casual vacancy to be filled by a person from the same party as the person who was “chosen by the people of the state”. That would not be Nash, as she was incapable of being chosen. Hughes would be the one who was technically “chosen by the people” and she was an endorsed candidate of the Liberal party at that time. So any replacement candidate, if she resigned, would have to be a Liberal party member.

Another constitutional oddity arises if Andrew Bartlett wins Larissa Waters’ seat on a recount. There is a possibility that he too might be disqualified, this time for holding an office of profit under the crown at the time of his nomination, because he was employed by a university. There is uncertainty about the status of university employees and whether their offices are “under the crown”. It may be different from state to state and university to university, depending upon the degree to which such officers may be the subject of ministerial direction or are given statutory independence from the crown.

The main message coming out of the high court’s decision, however, is that the disqualification provisions in the constitution are going to be strictly applied. We saw that already in relation to Senator Rod Culleton’s conviction, which was later annulled, but still caused him to be disqualified, and in relation to Senator Bob Day’s arrangements concerning his electorate office.

In the case of the citizenship seven, there was a good argument that if the purpose of the provision was to prevent split allegiances, then a person could not have a split allegiance if they did not know they were a citizen of a foreign country. The high court did not buy that argument. It considered that while the first part of the provision, concerning the “acknowledgement of allegiance” required a positive act and knowledge, the second part concerning being a citizen of a foreign power was merely a matter of legal status. That status is determined by foreign law and gives rise to legal duties. If a person has such a status, then with one exception, he or she cannot be chosen as a member of parliament until that citizenship has been renounced by following the steps required by the foreign law.

The exception is where a foreign country does not allow its citizenship to be renounced. The high court accepted that the constitution, in a separate section, expressly permits Australian citizens to become members of parliament and that it was not intended that they be irremediably prevented from participating in Australia’s system of representative government. In such a case, it is enough that a person has taken all steps that are reasonably required by the foreign law to renounce his or her citizenship where they are within his or her power.

The court focused upon certainty. It did not want to make distinctions concerning knowledge and subjectivity. It noted that a person’s knowledge “can be conceived of as a spectrum that ranges from the faintest inkling through to other states of mind such as suspicion, reasonable belief and moral certainty to absolute certainty”. It did not consider that something as important as disqualification from parliament should turn on “conceptual and practical uncertainties” which “are apt to undermine stable representative government”. In short, it wanted to draw a clear line for the future, which is what it has done. Woe betide the candidate who oversteps that line in the future, now that all have been warned.