The following editorial appeared in the Los Angeles Times on Wednesday, Nov. 7:

In March 2010, the U.S. Supreme Court concluded that a defendant’s 6th Amendment right to counsel — and its implied right to effective counsel — is violated when defense lawyers fail to warn their noncitizen clients that a guilty plea to certain offenses carries a risk of deportation. Now, the court must decide whether that ruling should be applied retroactively to people convicted before it was issued. Justice and the court’s own precedents suggest that it should.

The case before the court involves Roselva Chaidez, a Mexican immigrant who had been living legally in Chicago with her children and grandchildren. In 2003, she pleaded guilty to mail fraud for falsely claiming to have been a passenger in a car involved in an accident. She was sentenced to four years’ probation. When she applied for citizenship in 2007, federal authorities discovered her conviction and moved to deport her. Chaidez countered by arguing that her defense attorney had failed to warn her about the deportation consequences of her case. Had she known, Chaidez argued, she would not have pleaded guilty but would have gone to trial or sought a plea agreement that didn’t result in her expulsion.

The justices must decide whether their 2010 decision, in Padilla v. Kentucky, should apply retroactively to Chaidez and others who were denied effective representation. The court has held that the determination about whether a ruling should be applied retroactively depends on whether it articulated a new legal principle or whether it merely applied an existing one. Padilla wouldn’t be the first landmark case to be applied only prospectively. In 1966, the Warren court rejected retroactive application of its famous Miranda decision, which held that arrestees must be informed of their rights.

But this case is different. The court moved incrementally and openly toward its Padilla ruling. In 2001, the justices noted that all reasonably competent lawyers would caution their noncitizen clients that a guilty plea could carry the risk of deportation. And in the Padilla decision itself, Justice John Paul Stevens, writing for the court, pointed out that for 15 years “professional norms” had imposed an obligation on counsel to provide advice about deportation consequences. He also strongly suggested that the Padilla rule would be applied retroactively when he discussed its effect on “convictions already obtained.”

There are obvious difficulties in applying new rules to old circumstances. Doing so invites abuse, and could burden state and federal courts with thousands of appeals, some undoubtedly frivolous.

Those concerns are legitimate but exaggerated. Some states, including California, already require defense attorneys to advise their immigrant clients about the deportation consequences of criminal cases. What’s more, those noncitizens who challenge their deportations would have to convince courts not only that they were not properly advised but that the result was harmful to them.

A finding that the Padilla ruling should be applied retroactively would hardly open a floodgate; more likely, it would protect a worthy few who had the misfortune of pleading guilty on the basis of bad advice before March 2010.