CPA does have a point - it shouldn't be illegal (and in fact it's probably unconstitutional) to bar a man from gainful employment anywhere he'd like to go. He has another point in that the reason it's so lucrative to buy these people off is that these regulatory bodies have immense power. Those are two statements I think we can agree are factual.
If you are of the opinion that these regulatory bodies are necessary, then the question becomes how to best firewall the regulators against outside influence. Banning those who were recently in power from then working in a related private sector area is supposedly done to deny use of special inside knowledge or contacts within government. Perhaps it would be better to simply compensate these top regulators better so that they will harder to bribe? Sounds odd but it could work.
It's funny that the same people who yell 'government is bad' are the same ones who demand policies that make government bad.
The Congressman who led Medicare Part D through Congress and resigned weeks later to head the lobbying for big Pharma left to a $2 million a year position.
So, we should pay all Congressmen $2 million a year?
Then again, Robert Rubin, who pushed so much Wall Street friendly de-regulation, left to be an executive at Citibank.
Oh, wait, our Treasury Secretaries have been coming from heading Goldman-Sachs.
So, let's pay our secretaries and senior economic advisors whatever they'd make as Citibank executives or heading Goldman Sachs.
I don't mean to be abrupt to what I assume are your sincere views on this, but you are quick to express a quite wrong opposition to a helpful policy on 'constitutional' grounds, in part. Those sorts of restrictions are not 'unconstitutional', any more than requiring confidentiality agreements by CIA employees are violations of free speech, regarding classified information. They're terms of employment voluntarily accepted.
There are real questions how best to do this - and we should recognize that people give up large amounts of money to serve in the government. Robert McNamara gave up a fortune as the head of Ford to join the government; Supreme Court Justices (and other judges) make a fraction of what they could as powerful private lawyers; some in Congress make far less to serve there (Ted Kennedy wasn't a Senator for the money).
But we do have terrible financial incentives now, even with the limited restrictions; hundreds of former members and staffers from Congress are now lobbyists, and current members and staffers, while they can't take bribes now, are aware of those opportunities that might be affected by what they do in office.
The unlimited corporate contributions, which can pay for expensive and massive ad campaigns that turn a corporate whore selling out the public into Abraham Lincoln in the ads, are another part of the problem and corruption. (Of course they can also turn Abraham Lincoln into Hitler).
It's hard to see how to keep public servants serving the public without limiting their being able to receive great rewards soon after from powerful interests.