Once again, the Government’s rationale comes up short.Cost is an important factor for agencies to consider in many contexts. But cheapness alone cannot save an arbitrary agency policy. (If it could, flipping coins would be avalid way to determine an alien’s eligibility for a waiver.) And in any event, we suspect the Government exaggeratesthe cost savings associated with the comparable-groundsrule. Judulang’s proposed approach asks immigrationofficials only to do what they have done for years in exclusion cases; that means, for one thing, that officials can make use of substantial existing precedent governing whether a crime falls within a ground of exclusion. And Judulang’s proposal may not be the only alternative to the comparable-grounds rule. See supra, at 11–12. In rejecting that rule, we do not preclude the BIA from trying todevise another, equally economical policy respecting eligibility for §212(c) relief, so long as it comports with everything held in both this decision and St. Cyr.

From Judulang v. Holder. Here, Kagan discounts the liberty cost–that is the cost to society and government by making it easier for aliens to avoid removal–and focuses on the safety cost–that is the cost to the individual liberty of the alien whose removal can be more easily effectuated through this arbitrary policy. Social cost. it’s everywhere!