The Supreme Court, in a 5-4 ruling on Tuesday in Sessions v. Dimaya, declared a provision of immigration law so vague as to be unconstitutional.

Noncitizens—including green card holders—can be deported for a conviction for what is known in immigration law as a “crime of violence.” The “crime of violence” deportation ground is considered as an aggravated felony under the immigration law. A noncitizen convicted of a crime classified as an “aggravated felony” is both deportable and ineligible for almost all relief from deportation.

A “crime of violence” is defined in several ways in immigration law. The definition which the Court struck down is a felony that “by its nature, involves a substantial risk” of physical force being used against a person or property. The Court found this provision virtually identical to a federal sentencing provision which it struck down as unconstitutionally vague in 2015 in the case known as Johnson v. United States.

A majority of the justices first agreed that the same standard the Court used for determining whether the criminal statute in Johnson was unconstitutionally vague applied to the civil deportation statute: whether the law gave ordinary people fair notice of the conduct it punishes.

In Dimaya, the vagueness of the phrase “substantial risk” ultimately doomed the statute because it did not allow noncitizens to understand what conduct would make them deportable. Because the statute defined a “crime of violence” as one which “by its nature” involved a substantial risk of force, immigration judges had to hypothesize an “ordinary” way in which the crime would be committed rather than considering the particular facts of an individual’s case.

To determine the “ordinary” way in which a crime was committed required judges to imagine how a crime might play out and then decide whether it would involve a “substantial risk” of force being used during the commission of the crime.

Quoting the criminal law in Johnson, the Court questioned how a judge was to determine what conduct a crime “ordinarily” involved—by “using a statistical analysis of the state reporter? A survey? Expert evidence? Google? Gut instinct?”

In Johnson, the late Justice Antonin Scalia described how a judge might have to decide whether “the ordinary burglar” would “invade an occupied home by night or an unoccupied home by day?”

One judge might conclude that an “ordinary burglary” involved a substantial risk of the burglar being discovered by the property owner and resorting to violence while escaping. On the other hand, another judge might conclude that the “ordinary burglar” would run away without doing anything violent if confronted by a property owner.

In Dimaya, the Court largely adopted earlier Supreme Court reasoning used in Johnson, concluding that the deportation provision was equally vague. Both cases essentially came down to the issue of how a judge could determine what crimes “by their nature” involve a substantial risk of force. The Court found this inquiry so vague as to leave the decision to a judge’s “gut instinct.”

Because the law hinged on a judge’s “gut instinct” about what crimes led to deportation, it did not provide immigrants with fair notice. As a result, the Court struck down the provision as unconstitutionally vague.

Following Tuesday’s decision, noncitizens can no longer be deported on this basis, although they may still be deportable under a different ground of the immigration law. If these individuals have not committed any other aggravated felony, they will likely now be eligible to seek relief from removal and will be able to ask an immigration judge to give them a second chance in the United States.