Having said all that, there are clearly times when shareholder activism boarders on an actionable offense. We may be witnessing such a public display right now. It may be instructive both to ERISA and SEC fiduciaries as well as the regulators themselves.

I recently caught the tail end of an interview on TV. It was white noise until I heard the subject claim he had a "fiduciary" duty to take the action he was taking. The subject was New York City Comptroller John Liu and the action he and the leaders of New York City's pension funds were taking involved using the pension plans 4.7 million shares to make a statement by voting against Wal-Mart incumbent directors at the upcoming annual meeting. Liu cited the immediate concern over Wal-Mart was allegations the company did nothing to stem the bribes offered to Mexican officials in order to facilitate store openings in that country.

It's not unusual for foreign countries to "require" what we in America call "bribes" before allowing a company to engage in business in that country. On the other hand, making such payments is illegal under U.S. law. But our argument had nothing to do with this controversial behavior on the part of both domestic and foreign governments. Our focus is on fiduciary responsibility.

Liu's strained claim that he had a fiduciary duty to vote against the Wal-Mart directors invites an interesting question: Does Wal-Mart actions hurt the long-term interests of its shareholders? Liu claims it does and even says he's been concerned about Wal-Mart's corporate decision-making ever since 2005, when the company agreed to pay a fine resulting from an investigation that it hired undocumented aliens. 

But a look at the record does not support Liu's claims. Wal-Mart stock – the measure of long-term interest for shareholders – has risen on par with the S&P 500 since the 2005 fine. Clearly, agreeing to pay the fine, while possibly hurting shareholders in the short-term (the stock underperformed versus the S&P from 2005-2008), both it and the index have returned almost 20 percent from 2005 through April 21^st. Of course, these figures only represent price returns and do not reflect dividends. Wal-Mart currently pays a dividend of 2.7 percent compared to a 2011 S&P dividend of 2.1 percent (per Forbes).

What's so important about April 21^st? That was the day the New York Times came out with their story about the bribery charges. Over the next four days, Wal-Mart shares lost 8 percent while the S&P remained flat. Since then, the company has kept pace with the S&P. 

Which brings us back to Liu, who admits he's had Wal-Mart on his radar since 2005. Let's, for a moment, assume the New York City pension plan held Wal-Mart since 2005. It's clear Wal-Mart suffered in the short-term due to the undocumented alien scandal. It's equally clearly Wal-Mart more than made up for that short-fall over the long-term.

What, exactly, is Liu's – or any other retirement plan trustee's – fiduciary duty to the plan and its beneficiaries? It's to act solely in the best interests of the plan's participants. That means investing in a manner to help employees meet their long-term retirement needs. In other words, it means, ideally, selling stocks before they underperform and buying them before they outperform.

In the case of Wal-Mart, if your investment policy encourages portfolio turnover, it meant selling in 2005 and buying in 2008. If you investment policy statement does not encourage portfolio turnover, an argument could be made holding onto Wal-Mart in 2005 was not a bad idea.

What clearly is a bad idea is Liu's intended actions. It looks like he either failed to execute (i.e., sell) Wal-Mart prior to the April 21^st New York Times article as his investment policy statement might have demanded, or he is using beneficiary assets to make a political statement. If the first case is true, Liu has breached his fiduciary duty by failing to properly monitor plan assets. If the latter case is true, Liu has breached his fiduciary duty by using his position as trustee of pensioner assets to promote a personal agenda that is not in the best interests of the beneficiaries.

As a retirement plan trustee, your fiduciary duty is to manage the assets in a manner that meets the needs of the plan's beneficiaries. It doesn't not mean to engage in political grandstanding. The only acceptable form of shareholder activism for a fiduciary is to vote with your feet. If this asset won't help the long-term interests of the beneficiaries, sell it and spend plan resources to find a suitable replacement, not complain about a bad pick.

Disclosure: I own a boutique investment adviser and some of my clients own Wal-Mart. This article is not a recommendation to buy or sell Wal-Mart or any other stock. This article is solely about fiduciary responsibility.