533US2 Unit: $U87 [10-21-02 18:35:10] PAGES PGT: OPIN Cite as: 533 U. S. 678 (2001) 697 Opinion of the Court We cannot find here, however, any clear indication of congressional intent to grant the Attorney General the power to hold indefinitely in confinement an alien ordered removed. And that is so whether protecting the community from dangerous aliens is a primary or (as we believe) secondary statutory purpose. Cf. post, at 706, 708–709 (Kennedy, J., dissenting). After all, the provision is part of a statute that has as its basic purpose effectuating an alien’s removal. Why should we assume that Congress saw the alien’s dangerousness as unrelated to this purpose? The Government points to the statute’s word “may.” But while “may” suggests discretion, it does not necessarily suggest unlimited discretion. In that respect the word “may” is ambiguous. Indeed, if Congress had meant to authorize long-term detention of unremovable aliens, it certainly could have spoken in clearer terms. Cf. 8 U. S. C. § 1537(b)(2)(C) (1994 ed., Supp. V) (“If no country is willing to receive” a terrorist alien ordered removed, “the Attorney General may, notwithstanding any other provision of law, retain the alien in custody” and must review the detention determination every six months). The Government points to similar related statutes that require detention of criminal aliens during removal proceedings and the removal period, and argues that these show that mandatory detention is the rule while discretionary release is the narrow exception. See Brief for Petitioners in No. 00–38, at 26–28 (citing 8 U. S. C. §§ 1226(c), 1231(a)(2)). But the statute before us applies not only to terrorists and criminals, but also to ordinary visa violators, see supra, at 691; and, more importantly, post-removal-period detention, unlike detention pending a determination of removability or during the subsequent 90-day removal period, has no obvious termination point. The Government also points to the statute’s history. That history catalogs a series of changes, from an initial period (before 1952) when lower courts had interpreted statutory