detainer

The right to keep a person, or a person's goods or property, against his will; a type of custody.

On Monday, the federal Immigration and Customs Enforcement agency placed a similar detainer on Melvin Jovel, 18, who on Sunday was the sixth person to be arrested in the case.

Through January, immigration authorities placed detainers on an additional 1,468 people — giving federal agents the right to hold suspects who are released from jail. […] Scott Weber, the field office director for the enforcement office in Newark, said that in roughly a third of the cases, his agency would file a detainer or immigration charges; another third involved individuals who could be deported after their court cases; and the rest might be United States citizens or legal residents.

One who detains.

[…] he chatted gaily with his fair detainer, showing no inclination to escape from the bondage in which she sought to retain him.