A central proposition on which much of normative economics is founded asserts that if two or more adults voluntarily agree to an exchange or trade and this does not have a negative fall-out on others, then government should not stop this exchange. Yet, on a variety of matters (hazardous work, the right to give up trade union rights in order to work in an export-processing zone) we tend to justify government or international interventions banning seemingly voluntary exchanges. This lecture will explore the meaning of coercion and voluntariness and try to articulate general principles for describing certain markets as 'obnoxious'. The principles will be applied to different labor market problems, ranging from sexual harassment to hazardous work.