Business Opinion: It was a dramatic end to one of the more turbulent chapters of US corporate history. Ken Lay, the impoverished preacher's son who rose to become a leading light of the US business community and a man with the ear of presidents, was ultimately revealed to be the most venal of creatures - a man who played carelessly with the well-being of others to suit the purposes of his own ego and greed.

His recent convictions for conspiracy and fraud in the multi-billion-dollar collapse of Enron may now be stricken from the record along with the prospect of his victims seeing him serve out the balance of his days in prison. Yet Lay does leave behind a significant legacy and one that is far from what he would have expected just five short years ago.

Lay was famous for his support for various charitable causes and the Republican party of president George W Bush. Yet, in the end, he left thousand of his employees without work and with significant holes in their retirement funding.

If anything, he left Bush's Republican-led Congress with a bigger headache. The collapse of Enron put business and its oversight firmly under the microscope and the most business-friendly administration of recent times was forced to enact the sort of legislation that runs diametrically counter to the views it holds and encourages - most notably the Sarbanes-Oxley Act.

Lay and Enron were not alone of course. There was Ebbers and Worldcom, Kozlowski and Tyco International, and plenty of others. But Enron and the cavalier behaviour of its executives has become a synonym for a malaise in corporate USA.

And there has been fallout. Closer to home, Irish drug company Elan was brought to its knees as rattled investors sold off stock when less-forgiving financial oversight publicised the presence of significant off-balance-sheet debt at the group.

Ultimately, Lay's legacy has been a sundering of trust between business and those who invest in it. And the price of that legacy has been a significant increase in the amount and cost of regulation that business is forced to undertake.

The question is whether business has learned that lesson. Sarbanes-Oxley, in the words of the US regulator, the Securities and Exchange Commission (SEC), introduced "reforms to enhance corporate responsibility, enhance financial disclosures and combat corporate and accounting fraud".

Although the act was less than four years old, there was already a concerted move within the US, even ahead of the Enron trial, for a watering down of its provisions. The US Chamber of Commerce has warned as recently as May that, without reform, the US could lose its leading position in global capital markets.

The telling elements of Sarbanes-Oxley were the provisions that hold company leaders accountable for the accuracy of the financial statements they release to the market and require companies to certify and document the effectiveness of their internal controls. Chief executives and chief financial officers have to sign to aver the accuracy of the figures.

In one move, the US congress returned corporate responsibility to where it rightly lies, with a company's top executives. There would be no more pleading of ignorance and shifting blame to underlings.

Of course, Sarbanes-Oxley has been inconvenient. Along with new accounting rules worldwide, it has raised the cost of doing business.

And it is not just US businesses that are affected. While European companies listed in the US have enjoyed two deferrals, they are now facing imminent reporting requirements.

But stricter oversight has proven to be the cost of restoring public confidence in the probity of business, which needs investor funding to fuel growth. Without that confidence, markets simply cannot operate effectively - and the market, ultimately, must be bigger than the needs of any one company or group.

Yes, at times, the rules are clumsy instruments, as continual amendment and court challenges in the Irish market and others have shown. Ultimately, however, any regulation and any regulator is only as good as they are allowed to be. The rules are there because they have been shown to be necessary.

The vast majority of businesses, listed and otherwise, are scrupulous in observing their responsibilities and the law. But that is not uniformly the case, even now.

Regardless of the shortcomings in resources and lack of efficiency by regulators, it must not be forgotten that the regulators have not been responsible for defrauding investors. That has been entirely the fault of the criminal intent of people within certain companies and, in some cases, their advisors.