A federal appeals court ruling could add to the number of inmates with legal grounds to seek reduced sentences because of a shifting interpretation of sentencing guidelines and what constitutes a violent crime.

The 4th U.S. Circuit Court of Appeals invalidated last week a 31/2-year sentence for Jose Herbert Henriquez, an El Salvadoran who pleaded guilty to illegally re-entering the United States. The lengthy sentence was based in part on a previous burglary conviction.

"A Maryland conviction of first-degree burglary cannot constitute a crime of violence," Judge James A. Wynn Jr. wrote for the majority, remanding the case to a lower court for Henriquez to be resentenced.

The finding follows a Supreme Court decision that gave judges new instructions on how to determine which state laws should count as violent. That finding and a subsequent appeals case has led to dozens of federal inmates from Maryland challenging their sentences, and Wynn's decision raises the possibility of further challenges.

Prosecutors say the technical rulings threaten to undermine efforts to impose long sentences and keep the public safe, but inmate advocates say prisoners who have been unjustly locked away for too long are finding hope in the string of court victories.

Matthew G. Kaiser, an attorney who writes about appellate cases, said Wynn and the 4th Circuit appear to be paying close attention to issues the Supreme Court examined in its ruling from last year on California's burglary law. Kaiser said Wynn's opinion could be used to bolster defense attorney's arguments in other kinds of cases, too.

"Massive amounts of prison time hang in the balance," Kaiser said.

Rod J. Rosenstein, the U.S. attorney for Maryland, said that while the sentencing guidelines have an important role and are designed to provide certainty and uniformity, cases now often devolve into protracted legal battles.

In Henriquez's case, the dispute was over a fine point: The meaning of the same crime in two different legal contexts.

"We are arguing about whether a conviction for burglary of a dwelling is a conviction for burglary of a dwelling," Rosenstein said.

The cases center on the role of federal statutes as well as sentencing guidelines, which provide judges with a range of recommended sentences based on the seriousness of an offense and other factors.

The trial judge court in the Henriquez case considered a 12-year-old burglary conviction on his record as one of the factors, which greatly increased the sentence he faced because the judge ruled that it was a "crime of violence."

At his sentencing in federal court in Greenbelt, Henriquez's attorneys argued over the burglary issue but also urged the judge to take into consideration other circumstances and impose a shorter sentence.

Henriquez came to the United States as a teenager and had a daughter who was born here, according to court documents. But in 2002, he was deported after a series of run-ins with the law that ended with the burglary conviction, and he spent the next 10 years working with his father tending cattle in El Salvador before deciding to return to America to be reunited with the daughter, his eldest child.

"I would like to apologize for having returned illegally to this country," Henriquez said at his sentencing, according to a transcript. "But the reason I came back was to get to know my daughter who I haven't seen since she was very small."

His lawyers asked for a sentence of 14 to 18 months.

Prosecutors pointed out that Henriquez had other convictions on his record and that a longer sentence would serve to deter people who come to the country illegally and then commit crimes.

The court agreed, calling Henriquez "not exactly a model citizen," according to the transcript, and imposed a 41-month sentence.

Henriquez will now have a fresh chance to go before a judge.

The reason can be traced to a complicated interpretation of language and law.