Washington » Immigrants have a constitutional right to be told by their lawyers whether pleading guilty to a crime could lead to their deportation, the Supreme Court said Wednesday.

The high court's ruling extends the Constitution's Sixth Amendment guarantee of "effective assistance of counsel" in criminal cases to immigration advice, especially in cases that involve deportation.

"The severity of deportation -- the equivalent of banishment or exile -- only underscores how critical it is for counsel to inform her noncitizen client that he faces a risk of deportation," said Justice John Paul Stevens, who wrote the opinion for the court.

The decision puts a new burden on lawyers to advise immigrant clients about the consequences of a guilty plea, although more than 20 states already require some degree of notification. Twenty-seven states also say the cost of providing lawyers for poor immigrant defendants will skyrocket because the states could also have to pay for immigration advice.

The ruling came in the case of Jose Padilla, who was born in Honduras. Padilla asked the high court to throw out his 2001 guilty plea to drug charges in Kentucky, which made his deportation virtually mandatory.

Padilla, who has lived in the United States for more than 40 years as a legal permanent resident, said he asked his lawyer at the time whether a guilty plea would affect his immigration status and was told it wouldn't. But Padilla's trial lawyer was wrong. He now faces deportation.

His lawyer for the appeal told the Supreme Court that the incorrect information given Padilla was a violation of the Sixth Amendment right to "effective assistance of counsel."

The Supreme Court's majority agreed.

"It is our responsibility under the Constitution to ensure that no criminal defendant -- whether a citizen or not -- is left to the 'mercies of incompetent counsel,'" Stevens said.