By Lawrence Hurley and Jonathan Stempel

WASHINGTON, Feb 20 (Reuters) - The U.S. Supreme Court declined on Wednesday to apply retroactively a 2010 ruling that requires lawyers to tell immigrant clients that they can be deported if they plead guilty to certain crimes.

The 7-2 decision was a defeat for thousands of immigrants who might have been able to withdraw guilty pleas in cases alleging ineffective counsel.

These cases predated the court's March 2010 ruling in Padilla v. Kentucky that immigrants should be told some consequences of guilty pleas.

In Wednesday's majority opinion, Justice Elena Kagan said the Padilla ruling did not apply to cases that were already final after an appeal.

She said it would not have been apparent to a typical judge before that ruling that the Sixth Amendment right to a competent lawyer extended to advising immigrants about deportation risks.

"So when we decided Padilla, we answered a question about the Sixth Amendment's reach that we had left open, in a way that altered the law of most jurisdictions," she wrote.

Under court precedent, such a shift in the law does not apply to defendants whose convictions became final before the ruling came down, she added.

Justice Clarence Thomas concurred in the judgment, saying he still believed that Padilla, from which he dissented, was wrongly decided.

Justice Sonia Sotomayor wrote a dissenting opinion, saying the 2010 decision was not as much as a shift in the law as Kagan claimed, in part because lawyers are now better trained in how immigration laws affect their clients.

"The only difference from prior law was that the underlying professional norms had changed such that counsel's failure to give this advice now amounted to a constitutionally deficient performance," she wrote. Justice Ruth Bader Ginsburg joined Sotomayor's dissenting opinion.

QUESTION LEFT OPEN

Stanford Law School professor Jeffrey Fisher, who argued the case for Chaidez, was disappointed with the decision but said the court left open whether the Padilla ruling could apply to other post-conviction claims in federal court.

In a footnote, Kagan said the court declined to rule on whether precedents on retroactivity applied to challenges to federal, as opposed to state, convictions, and in particular ineffective assistance of counsel claims in federal cases.

Chaidez herself can raise that point when the case is remanded back to the district court, Fisher said.

Stephen Kinnaird, who filed a brief on behalf of the National Association of Federal Defenders in support of Chaidez, said it was a "close question" whether the Padilla case constituted a new rule.

But he said Padilla has led to a "reformation of lawyer conduct," with immigration consequences now much more likely to be addressed during plea bargaining.

GUILTY PLEA

Wednesday's case involved Roselva Chaidez, a Mexican citizen and lawful permanent U.S. resident in Chicago.

The government in 2009 ordered her removed from the country in light of her guilty plea six years earlier for mail fraud in an automobile insurance scheme.

Chaidez had disclosed the plea while trying to become a naturalized citizen. She said the removal was unfair because her lawyer in the criminal case had never told her that she could be deported for pleading guilty.

Kent Scheidegger, a lawyer at the nonprofit pro-prosecution Criminal Justice Legal Foundation, said the court's decision on Wednesday avoids a potential logjam of appeals by immigrants in the lower courts.

"Going back and reconsidering all these cases would have been a serious problem," he said. "It's always easy to go back and challenge the advice you got five years ago."

The case is Chaidez v. United States, U.S. Supreme Court, No. 11-820.

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