When President Biden took office, the Department of Homeland Security issued new Guidelines for immigration enforcement. The Guidelines prioritize the arrest and removal from the United States of noncitizens who are suspected terrorists or dangerous criminals, or who have unlawfully entered the country only recently, for example. Ps sued the Department of Homeland Security. Ps want the Federal Judiciary to order the Executive Branch to alter its arrest policy so as to make more arrests. Ps claim the Guidelines contravene two federal statutes that purportedly require the Department to arrest more criminal noncitizens pending their removal. Ps contend that for certain noncitizens, such as those who are removable due to a state criminal conviction, §1226(c) of Title 8 says that the Department “shall” arrest those noncitizens and take them into custody when they are released from state prison. Second, §1231(a)(2), as Ps see it, provides that the Department “shall” arrest and detain certain noncitizens for 90 days after entry of a final order of removal. Ps claim that D's failure to comply with those statutory mandates imposes costs on them. The States assert, for example, that they must continue to incarcerate or supply social services such as healthcare and education to noncitizens who should be (but are not being) arrested by the Federal Government. Based on those costs, the District Court determined that Ps have standing. On the merits, the District Court ruled that the Guidelines are unlawful, and vacated the Guidelines. The U. S. Court of Appeals for the Fifth Circuit declined to stay the District Court’s judgment. The Supreme Court granted certiorari.