Explanation

In an investment policy statement (IPS), constraints are typically categorized into several types:

1. Legal and Regulatory Constraints: These are requirements imposed by laws, regulations, or governing bodies that must be followed.
2. Tax Constraints: These relate to an investor's tax situation and how it affects investment decisions.
3. Unique Circumstances: These include personal preferences, ethical considerations, or other specific requirements.

Let's analyze each option:

A. An investor's tax status - This is a tax constraint, not a legal/regulatory constraint. Tax status affects investment decisions (e.g., tax-exempt vs. taxable accounts, capital gains considerations), but it's not a legal requirement imposed by regulators.

B. A pension fund's self-investment limit - This is a legal and regulatory constraint. Pension funds are subject to specific regulations that limit how much they can invest in their own company's securities or related entities. These limits are imposed by regulatory bodies to ensure diversification and protect beneficiaries.

C. An investor's desire to avoid investments in the gambling industry - This is a unique circumstance or ethical constraint. It reflects personal values or preferences, not a legal requirement.

Key Distinction:

• Legal/regulatory constraints are mandatory requirements imposed by external authorities.
• Tax constraints relate to optimizing after-tax returns within the legal framework.
• Unique circumstances are voluntary restrictions based on personal preferences.

Therefore, option B is the correct answer as it represents a constraint imposed by legal or regulatory authorities on pension funds.