Classic arbitrage involves the same asset selling at different prices; the leverage rule arbitrage we study here involves assets of different risk levels requiring the same amount of capital. The supplementary leverage ratio (SLR) rule, finalized by U.S. regulators in September 2014, requires a minimum ratio of capital to assets at the largest U.S. banks. The floor is higher for more systemically important banks, but not for banks with riskier assets. That non-risk-based aspect of SLR was intentional, since the leverage limit was meant to backstop (“supplement”) risk-based capital rules in case banks underestimate their asset risk and overstate their capital strength. As policymakers have noted and bankers have warned, if the leverage rule is the binding capital requirement, banks can “arbitrage” the rule by selling safer assets and replacing them with riskier, higher-yielding ones. The findings of our recent staff report are consistent with those concerns.