When regulation protects narrow interests – usually the interests of the incumbent industry – at the expense of the public interest. Capture occurs in various ways: from straightforward bribes and threats, to more implicit quid pro quos such as the lucrative future employment (revolving door), to softer forms of cognitive/cultural capture.
“… as a rule, regulation is acquired by the industry and is designed and operated primarily for its benefit.” George Stigler – The Theory of Economic Regulation (1971)