Since the Supreme Court’s 2010 decision in Citizens United v. Federal Election Commission, holding that corporations and unions have a right to make expenditures in political races, the political left has been frantically trying to find some way to silence corporate voices.

The latest ploy is an effort to convince American businesses to voluntarily disarm and leave the playing field to unions and foundation-funded lobbying groups. Leading this effort is an organization called the Center for Political Accountability (CPA).

The center says its role is to “address the secrecy that cloaks much of the political activity engaged in by companies and the risks this poses to shareholder value.” In fact, it seems more interested in making sure companies do not engage in political activity even when doing so might increase shareholder value.

CPA argues that political involvement is risky for corporations. Its president, Bruce Freed, a former Democratic congressional staffer, likes to cite the example of Target. In 2010, Target contributed to Minnesota Forward, a group focused on budget and tax issues in the state where Target is headquartered. Minnesota Forward ran ads supporting Tom Emmer, a low-tax Republican, for governor.  .

Mr. Emmer also supported a ban on same-sex marriage, and the Human Rights Campaign, a gay rights organization which supported Mr. Emmer’s opponent, criticized Target for the contribution. MoveOn.org then announced a boycott of the chain, which was previously known for its gay-friendly human resources policies. The boycott fizzled and had no effect on Target’s stock price, but CPA has nevertheless seized on this episode as evidence of the “dangers” of corporate political involvement.

On Oct. 28, CPA and the Zicklin Center for Business Ethics at the Wharton School at the University of Pennsylvania released a so-called “CPA-Zicklin Index” of companies’ compliance with “best practices” for corporate political spending. These “best practices,” in turn, come from the Conference Board’s 2010 Handbook on Corporate Political Activity, a report co-authored by—surprise!—CPA’s Mr. Freed. It includes no fewer than 29 measures intended to hinder corporate political strategies.

For example, the CPA-Zicklin Index rates companies high if they “restrict political spending.” However, if a corporation insists on political spending, it is rewarded if it only spends through the cumbersome, expensive means of a Political Action Committee, or PAC—exactly the requirement that Citizens United did away with.

CPA’s “best practices” reward corporations that further hamstring themselves with rules such as mandating a committee of outside directors to oversee political spending (including trade-association dues) and to approve each expenditure in advance. They would also insist that companies make financial disclosures in excess of those required by law, even if doing so would not be in the company’s interest as determined by the board or management. These would include disclosure of personal contributions by corporate managers and directors, requiring the company to monitor its managers’ personal political activity.

Mr. Freed’s co-authors on the CPA-Zicklin Index—all now affiliated with CPA—are a former analyst for the Service Employees International Union (SEIU), a writer who also works for the George Soros-funded Justice at Stake (a group critical of business efforts to promote state-level tort reform), and a former general counsel to the Democratic National Committee. CPA’s chief financial officer was formerly Maryland coordinator for John Kerry’s presidential campaign. CPA’s funding comes almost entirely from the same liberal foundations that have long funded “campaign-finance reform” groups such as Public Citizen and Common Cause that opposed the Citizens United ruling, though not from any concern for the best interest of the business community.

Joining CPA’s efforts to persuade corporations to voluntarily surrender their First Amendment rights are various “social investor” funds, most notably NorthStar Asset Management and Walden Asset Management.

Like CPA, these new “activist” investors claim that their proposed restrictions on corporate political activity will actually increase value. But they don’t act as if they believe that to be true.

NorthStar, for example, urges its clients to divest themselves from targeted companies, retaining just enough shares to engage in corporate activism. In other words, they advise their own clients to limit their financial exposure to companies that might actually follow their recommendations. Presumably, if they thought their recommendations would increase profitability, they would buy shares to gain the windfall that would come with adoption of their proposals.

NorthStar’s activism has included efforts to restrict corporate political engagement, opposition to increases in corporate pay, demands for corporations to recognize a “human right to water,” and opposition to genetically modified foods.

Walden Asset Management, meanwhile, has long worked with the American Federation of State, County and Municipal Employees (AFSCME) and the SEIU to file shareholder resolutions. It has demanded that executive compensation be tied to “social criteria” and that companies adopt International Labor Organization standards. In 2010, it sent a letter to corporate executives—co-signed by CPA’s Mr. Freed—urging them to cease support for the U.S. Chamber of Commerce and the National Association of Manufacturers because it disagreed with those organizations on environmental issues.

In short, while purporting to be looking out for business interests, CPA and its allies appear more interested in a partisan political agenda and unilateral political disarmament by the business community. Citizens United did not, after all, apply only to business corporations, but also to unions and advocacy corporations such as environmentalist and anti-trade groups. Their spending will remain unabated after corporate America adopts Mr. Freed’s “best practices.” It is as if a GOP operative were to announce “best spending practices” for labor unions. Who would take that seriously?

Decisions about political activity are like any other business decisions. They involve risk, and they involve careful consideration of numerous factors, all the while bearing in mind the duties owed to shareholders. Corporate managers and boards cannot escape their obligations by adopting blanket policies authored by those who do not have their best interests at heart.

Mr. Smith is a professor at Capital University Law School and chairman of the Center for Competitive Politics.