The DA has argued in the Western Cape High Court that Patricia de Lille showed clear intention to resign from the party during a radio interview conducted in late April.
The DA and De Lille met in the High Court on Tuesday for day two of De Lille's application to have the party's "determination" to cease her membership set aside.
De Lille was deemed to have breached a clause in the DA's constitution that states that if a member publicly declares his or her intention to resign from the party, they cease to be a member.
Advocate Sean Rosenberg, SC, argued for the DA that De Lille did just that during the infamous Radio 702 interview in question with host Eusebius McKaiser on April 16.
Towards the end of the of the interview, McKaiser tried to sum up De Lille's position regarding her intention to leave the party upon clearing her name during a disciplinary process.
De Lille said: "I will walk away, you have summed it up correctly."
Relationship has 'irretrievably broken down'
"From the radio interview, it's clear Ms De Lille's only intention to remain in the party was to clear her name," Rosenberg argued on Tuesday.
"There is no real intention to restore the relationship with the DA."
McKaiser qualified his questions repeatedly, expressing clearly that his question related to her membership of the party, De Lille agreed in principle, Rosenberg continued.
It was also clear from the interview that the relationship between De Lille and the party had "irretrievably broken down".
De Lille was, therefore "holding on to her membership" merely for her own interests and not for the mutual contract that both parties entered into, he argued.
De Lille's counsel argued on Monday that the mayor meant she would resign from her mayoral seat, not the party.
Judge Pearl Mantame asked whether the DA's determination that she had resigned was "premature", given De Lille's condition that she first clear her name.
Rosenberg rejected that, saying De Lille's words only meant that "she would resign when it suits her". She still intended to resign effectively, he argued.
Judges Mark Sher and Andre Le Grange quizzed Rosenberg on the DA clause in question and wondered whether it made allowances for conditional resignations.
Rosenberg responded that it was up to the court to decide whether there was a clear, express indication that the member wanted to resign from the party.
Ultimately, the DA's cessation clause was designed to ensure public commitment from its members, and to protect the party from disloyal members, he said.
"The emphasis here is on a public declaration or commitment. A person who declares their intention [to leave the party] in public can't be relied upon.
"A public declaration is different to a personal or private intention to resign."
Members bound by party rules
Another of Rosenberg's main points was that the law allowed political parties to conduct their processes themselves.
A member and a party enter into a mutual contract upon joining and are bound by the party's internal rules.
Rosenberg said that political parties elected leaders to represent them at councils or legislatures, and that if they lose their membership, "they can't represent the party".
Having run on a DA ticket, De Lille can't hold on to special rights when it came to holding office.
Her argument that there must be a "good reason" to remove her, "is simply not true". If the party wishes to remove its member, it can do so, he said.
Judge Le Grange noted that the question was not whether the party can remove her, but whether that removal should be within the constraints of the Promotion of Administrative Justice Act, in the case of public office bearers.
Le Grange and Sher summed up the problem before the courts. It was clear there was a statement by De Lille to resign, but it needed to be answered whether it was from the mayoral seat or the party and whether the DA's clause makes allowances for conditional intention to resign.
Sher asked what would have happened had De Lille said she would resign when she turned a certain age. "Would that have been enough for her membership to cease now, today?"
In response, Rosenberg said it was up to the court to decide those questions, and their contention was that De Lille showed a clear intention to resign, whether it was conditional or not.
Arguments continued on Tuesday afternoon.