Isn't all legislature a response to something that violated the public's trust?
I think that's an ideal rationale for legislation... unfortunately, there is a lot of legislation passed that enables unfortunate breaches of the public's trust. Consider the Glass Act (also known as the Glass-Steagall Act). This is the 1933 law sponsored by Carter Glass (D-Va.) and Henry Steagall (D-Ala.) that created the Federal Deposit Insurance Corporation and introduced several major banking reforms that were largely focused on reducing the ability for banks to speculate. Of course, this was a response to the 1929 Crash and someone, somewhere looked at the aftermath of the Crash and vowed "never again".
In the 1980s, a lot of people were agitating for repeal of Glass-Steagall saying that it was dated, it impeded competition and that conflicts of interest existed despite the legislation. In the late 90s, Phil Gramm (R-Tex.) and Jim Leach (R-Iowa) sponsored legislation that became the Gramm-Leach-Bliley Act after Tom Bliley (R-Va.) threw his support behind the bill. With that legislation, the Financial Services Modernization Act of 1999 came into being. The ensuing bump in the markets probably caused someone, somewhere to look at Glass-Steagall and vow "never again".
So, what started as legislation to address a breach of the public's trust was eventually thwarted by legislation that ultimately breached the public's trust. No doubt, in both cases, the players were attempting to protect what they thought were the best interests of the public at large and ensure the public's trust in our institutions. However, in retrospect, it's clear to see somebody got it wrong and decided the interests of the few outweighed the interests of the many. Funny old world.