Ring-Fencing

In a regulatory context, the term can best be understood as legally deconstructing a firm in order to more optimally reallocate and reduce risk. So utilized, ring-fencing can help to protect public-benefit activities performed by private-sector firms, as well as to mitigate systemic risk and the too-big-to-fail problem inherent in large financial institutions. If not structured carefully, however, ring-fencing can inadvertently undermine efficiency and externalize costs.

Source: https://scholarship.law.duke.edu/faculty_scholarship/2855/