The critique suggesting that morality alone is inadequate for effective legislation stems from which legal theory?

Legal positivism is the correct answer because it emphasizes that law should be understood through its social facts and established procedures rather than merely through moral considerations. This theory posits that laws are valid if created according to prescribed rules, regardless of their moral content.

In contrast to natural law theory, which asserts that laws must align with moral principles, legal positivism critiques the assumption that morality should or does determine what the law is. This perspective recognizes that legislation can be influenced by various factors, including political, social, and economic conditions, indicating that moral considerations alone might not be sufficient for effective and enforceable laws.

Critical legal studies and Marxist theory provide important insights into the relationship between law and social justice or power dynamics, but they do not directly encapsulate the critique regarding morality's inadequacy in law-making as clearly as legal positivism does.