Immigrants who are in the US legally need not be automatically deported for minor drug offenses, the Supreme Court ruled Monday in a unanimous decision. The case, Carachuri-Rosendo v. Holder, involved a Texas man who was a permanent resident of the US, having lived here since he was five years old, who was ordered deported after a second minor drug conviction.

Jose Angel Carachuri-Rosendo was arrested for misdemeanor marijuana possession in Texas in 2004 and served 20 days in jail. The following year, he was arrested again, this time for possessing a single Xanax tablet without a prescription, and sentenced to 10 days in jail.

That too was a misdemeanor offense. But federal prosecutors argued that Carachuri-Rosendo's Xanax bust amounted to an "aggravated felony" under federal immigration law, making his deportation mandatory. Under federal immigration law and a previous Supreme Court ruling, federal prosecutors can charge a second drug offense as an "aggravated felony," a policy that has led to near life-long residents of the US being deported to countries they never knew over small-time drug busts, even petty marijuana busts.

Although, the prosecution theory prevailed in the lower courts, the Supreme Court shot it down this week. Complaining that the interaction of various state and federal laws created "a maze of statutory cross-references," Justice John Paul Stevens, writing for seven justices, displayed the sort of common sense too often missing in recent Supreme Court decisions.

"We do not usually think of a 10-day sentence for the unauthorized possession of a trivial amount of a prescription drug as an 'aggravated felony.' A 'felony,' we have come to understand, is a 'serious crime usually punishable by imprisonment for more than one year or by death,'" Justice White wrote. "While it is true that a defendant's criminal history might be seen to make an offense 'worse' by virtue thereof, it is nevertheless unorthodox to classify this type of petty simple possession recidivism as an 'aggravated felony.'"

The ruling does not mean Carachuri-Rosendo is home free. He is still eligible for deportation, but under the ruling, he may now seek a discretionary waiver of deportation from the Attorney General.