ON FEBRUARY 27th, in the midst of a fresh crack-down on undocumented migrants and a pending revision of the president’s travel ban, the Supreme Court heard an immigration case with potentially wide-ranging implications. Esquivel-Quintana v Jefferson Sessions is the first Supreme Court case naming Donald Trump’s new attorney general as a party—though it concerns a matter that took place well before he joined the cabinet. Depending on how the justices rule, immigration authorities may soon either enjoy a freer hand to deport non-citizens or find themselves judicially constrained in these efforts.

Juan Esquivel-Quintana arrived in America from Mexico with his parents at the age of 12 and became a lawful permanent resident. In 2009, Mr Esquivel-Quintana served 90 days in jail and five years on probation for statutory rape. He was found to have violated California’s penal code by having sex, at the age of 20, with his 16-year-old girlfriend. (The law criminalises sexual relations between an adult and “a minor who is more than three years younger than the perpetrator”.) Later, after moving from California to Michigan, Mr Esquivel-Quintana became subject to removal proceedings by the Department of Homeland Security. The Immigration and Nationality Act (INA) provides that “sexual abuse of a minor” is an “aggravated felony” and constitutes grounds for deportation. Mr Esquivel-Quintana’s crime, authorities said, fit that bill.

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The case turns on the meaning of the phrase “sexual abuse of a minor”. Jeffrey Fisher, Mr Esquivel-Quintana’s lawyer, told the justices that his client’s actions would not have cost him a day in jail in 43 states. And of the seven remaining states, most construe sex with near-17-year-olds as a misdemeanor, “and only one of those seven states calls that conduct abuse”. On top of that, Mr Esquivel-Quintana’s behaviour would not have been a crime under either the Model Penal Code (a project in the 1960s to standardise state criminal laws) or federal law. In sum, Mr Fisher argued, the justices “could decide this case by saying that the seven states that have laws like California’s…but draw the age of consent at 18, automatically fall outside of sexual abuse of a minor”. Taking in the full “sweep” of state and federal law, Mr Fisher proposed, 16 ought to be accepted as the age of consent for the purposes of the INA.