533US2 680 Unit: $U87 [10-21-02 18:35:10] PAGES PGT: OPIN ZADVYDAS v. DAVIS Syllabus release conditions that may not be violated and their liberty interest is strong enough to raise a serious constitutional problem with indefinite detention. Pp. 692–696. (c) Despite the constitutional problem here, if this Court were to find a clear congressional intent to grant the Attorney General the power to indefinitely detain an alien ordered removed, the Court would be required to give it effect. But this Court finds no clear indication of such intent. The statute’s use of “may” is ambiguous and does not necessarily suggest unlimited discretion. Similar related statutes requiring detention of criminal aliens during removal proceedings and the removal period do not show that Congress authorized indefinite detention here. Finally, nothing in the statute’s legislative history clearly demonstrates a congressional intent to authorize indefinite, perhaps permanent, detention. Pp. 696–699. 3. The application of the “reasonable time” limitation is subject to federal-court review. The basic federal habeas statute grants the federal courts authority to determine whether post-removal-period detention is pursuant to statutory authority. In answering that question, the court must ask whether the detention exceeds a period reasonably necessary to secure removal. It should measure reasonableness primarily in terms of the statute’s purpose of assuring the alien’s presence at the moment of removal. Thus, if removal is not reasonably foreseeable, the court should hold continued detention unreasonable and no longer authorized. If it is foreseeable, the court should consider the risk of the alien’s committing further crimes as a factor potentially justifying continued confinement. Without abdicating their responsibility to review the detention’s lawfulness, the courts can take appropriate account of such matters as the Executive Branch’s greater immigrationrelated expertise, the Immigration and Naturalization Service’s administrative needs and concerns, and the Nation’s need to speak with one voice on immigration. In order to limit the occasions when courts will need to make the difficult judgments called for by the recognition of this necessary Executive leeway, it is practically necessary to recognize a presumptively reasonable period of detention. It is unlikely that Congress believed that all reasonably foreseeable removals could be accomplished in 90 days, but there is reason to believe that it doubted the constitutionality of more than six months’ detention. Thus, for the sake of uniform administration in the federal courts, six months is the appropriate period. After the 6-month period, once an alien provides good reason to believe that there is no significant likelihood of removal in the reasonably foreseeable future, the Government must furnish evidence sufficient to rebut that showing. Pp. 699–701.