The U.S. Supreme Court case Nielsen v. Preap in 2018 revolved around the interpretation of a federal law that mandates detention during deportation proceedings for non-citizens who have committed certain crimes. The plaintiffs, Mony Preap and others, were legal permanent residents who had served sentences for criminal convictions and then released; they argued that because they weren't immediately detained by immigration authorities after their release from criminal custody, they should not be subject to mandatory detention without bond hearings later on. However, the court ruled in favor of the government (5-4), stating that under federal immigration law, such individuals can be detained years after serving their sentences with no right to a bond hearing. This decision upheld broad authority of the Department of Homeland Security over when and how it detains immigrants for removal proceedings.

In the dissenting opinion for Nielsen v. Preap, Justice Stephen Breyer, joined by Justices Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan argued that the majority's interpretation of federal immigration law was too broad. They contended that mandatory detention without a bail hearing should only apply to immigrants who were detained promptly after their release from criminal custody, not those who had been living in communities for years or even decades since their release. The dissenters also pointed out potential constitutional concerns with indefinite detention without a hearing and emphasized Congress' intent to target dangerous individuals rather than subject all noncitizens convicted of certain crimes to mandatory detention regardless of individual circumstances or risks posed.