Mangosuthu Buthelezi has defied President Thabo Mbeki by agreeing to a court order to publish controversial immigration regulations.
This is one of several serious allegations made in papers before the Cape High Court by Mbeki, as the relationship between him and the home affairs minister hits an all-time low.
If Buthelezi got his way, Mbeki argued, drug dealers and human traffickers would find it easy to enter South Africa; it would be virtually impossible to deport illegal immigrants; and the country would be dumped into "administrative chaos".
Immigration regulations state who can come into South Africa and who must be kept out.
After almost a decade of acrimonious fights over the country's immigration policy, the two adversaries will finally square up in court next week.
This serious clash between the head of state and one of his cabinet ministers comes only two weeks before South Africa's third democratic elections, and amid fears of election violence between their parties - the African National Congress and Inkatha Freedom Party - in KwaZulu-Natal.
Buthelezi was completely ignored as a party by Mbeki in the papers, but he has already applied for leave to intervene.
In the papers, Minister of Justice Penuell Maduna, acting on behalf of Mbeki, said Buthelezi's consent to the court order - even though he knew the cabinet was still considering the regulations, and without telling Mbeki about it - "had no legal effect" and was "creating a potential constitutional crisis".
The drama started about a month ago when Cape Town immigration attorney Gary Eisenberg brought an application to force Buthelezi to publish final immigration regulations. These regulations were the product of public comment and the input of the Immigration Advisory Board.
Buthelezi agreed to publish the regulations, which were at that stage under discussion by the cabinet. By publishing them in the Government Gazette on March 8, he started a one-month countdown before the regulations were to come into operation.
Mbeki then rushed to court to obtain an order suspending the order to which Buthelezi had agreed. Even though this might have had some political impact, legal experts were divided over the effect it would have on the date that the published regulations were to come into operation.
In a bizarre twist, both the departments of Justice and Home Affairs then issued press releases.
The Department of Justice said the regulations were not coming into operation, while Home Affairs said they were.
Shortly afterwards, the president's legal team filed an amended court action, this time asking for the regulations to be declared invalid and of no force and effect.
In an affidavit filed with these papers, Maduna said Buthelezi's regulations were "incapable of proper implementation and are unconstitutional".
In an affidavit filed at the Cape High Court, Maduna said that by ordering Buthelezi to publish the documents, the Cape High Court had infringed upon the cabinet's constitutional authority.
The legal standpoint the president's team was taking was that Buthelezi "had no authority to fetter the power vested in him or the powers of the president and cabinet", argued Maduna.
Maduna said the order directly impacted on the departments of Foreign Affairs, Safety and Security, Justice, Correctional Services, Health, Education, Trade and Industry, Science and Technology, and Finance - but none had been asked about it.
According to Maduna's affidavit, the present regulations also violate bilateral agreements with a number of countries.
Maduna added that the regulations created "serious security risks" by allowing a "14-day grace period for foreigners and asylum-seekers".
"Passport holders from drug-producing countries ... regularly abuse travel facilitation," Maduna said.
He added that the regulations would make it almost impossible for people to be deported because immigration courts - for which provision is made in the regulations - would play a very important role in this process, but no measures had been put in place to create these courts.
Buthelezi knew that legal advisers were busy looking at the regulations, Maduna said, but had gone ahead and published them anyway.
"Administrative chaos and state liability will inevitably result from the confusion ..." Maduna said.
Mbeki's application is due to be heard on Monday.
The main objections are that the immigration regulations are unconstitutional and cannot be implemented successfully.
The new regulations are supposed to come into effect on April 8.
In addition, Minister of Justice Penuell Maduna claimed in papers before the court that: