Interest in sustainable investing is soaring, as more people become convinced that making a positive impact can be profitable as well as good for the planet and society. Unfortunately, the Labor Department doesn’t think these investments belong in your 401(k).

In June, the federal regulator proposed a rule that would restrict workplace retirement plans from investments that include environmental, social and governance considerations. Popularly known as ESG or socially responsible investing, this approach considers the sustainability of a company’s business practices.

The Labor Department says only returns, not business practices, should matter. But its proposal is unusual for a number of reasons, including its wide range of opponents. In my latest for the Associated Press, a look at how the opponents of sustainable investing could make things much more difficult.