The wheels of justice grind slowly in South Africa. But they are grinding. For years, former president Jacob Zuma has been the embodiment of impunity, emboldening others in positions of power to bend or break the law in pursuit of self-enrichment. Time and again, the man accused of using his presidency to effect a mass looting of state coffers through a process known as state capture has defied justice, weakening the very institutions charged with holding him and others to account.

This week, his years of evading justice may finally come to a close. If his last-minute appeals fail and if the police hold their nerve by arresting him, 79-year-old Zuma will be sent to jail for 15 months for contempt of court. Like Al Capone, Zuma would be imprisoned for a lesser crime, in his case refusing to give testimony to a commission of inquiry into state capture. That does not detract from the message it would send.

A prosecution over his alleged involvement in a corrupt arms deal in the 1990s is still trundling through courts. It may be years before he is tried over allegations of ransacking the state during his nine years as president to the benefit of a few and the impoverishment of the majority of black South Africans.

Still, the constitutional court’s ruling to send him to prison draws a line in the sand. In the year that South Africa’s post-apartheid constitution turns 25, it shows that the guardian of the constitution is still alive and kicking.

Zuma tried to erode its authority, as he has with other institutions from the prosecutor’s office to the tax agency, by predicting a popular uprising against what he called “judicial corruption”. Many South Africans are savouring the irony that his own arrogance in defying the court could land him in jail sooner than they dared hope, given his delaying tactics in his other legal cases.

In resisting his efforts to evade justice, the court quoted Nelson Mandela’s entreaty that it “stand on guard not only against direct assault on the principles of the constitution, but against insidious corrosion”.

Zuma’s imprisonment would send a signal to others, both inside and outside the ruling African National Congress, that no one is above the law, however powerful their connections or strong their support base. It would also bolster the faltering efforts of President Cyril Ramaphosa to clean up the ANC’s rank-smelling stable.

But in celebrating the constitutional court’s stand, one must not forget the lasting damage that Zuma has done. By cutting corrupt deals with business associates and hollowing out institutions designed to keep such practices in check, he has done irreparable harm.

Not only did he oversee nine years of economic stagnation in which income per capita actually declined and unemployment, particularly among the young, swelled. He also undermined the very legitimacy of the ANC as the party capable of delivering the economic benefits and social justice needed to heal the festering sores of the apartheid era. It is vital that Ramaphosa, who has a record of timidity, accelerates his efforts to purge the ANC of corruption.

At the eleventh hour there are signs the police are wobbling in their resolve to arrest Zuma. They should steel themselves and follow the court’s lead. Even if the law finally catches up with Zuma, it will be a necessary but insufficient start to rebuilding a semblance of hope in South Africa. Without a permanent end to cronyism, sustained economic growth and real opportunities for the mass of South Africans, it will not be enough.