Chen's escape in April set off a diplomatic tussle between Beijing and Washington before he was allowed to go to New York, where he is studying English and law and writing a memoir.
Chen's nephew Chen Kegui, 32, has been detained in China since May, accused of attacking local officials. The family says Chen Kegui acted in self-defense when the officials stormed into his house looking for his uncle and severely beat his parents.
Chen Guangcheng said Saturday that it was the local officials who broke law when they illegally entered his brother's house, smashing objects and beating people.
He added that his nephew has been locked up more than five months without access to his family and independent lawyers, a situation Chen called absurd.
"They have declared war on all forces of justice in the world and challenged the bottom line of morality," he said. "How can you say this is a society with rule of law?"
Chen learned from his brother Chen Guangfu, father of Chen Kegui, that prosecutors in Yinan county in eastern China's Shandong province had informed the family that police recommended charges of "intentional infliction of injury." The initial charge was the more serious attempted murder.
Family friend and New York University law professor Jerome Cohen said that prosecutors are highly likely to follow the police recommendation and that Kegui has slim chances of getting a fair trial.
"It's an evident case of injustice," Cohen said.
A man who answered the phone at Yinan county government Saturday evening said he had no information before he hung up. A woman who answered the phone at Yinan county's public safety bureau also said she had no information about the case.
Chen Guangcheng called for public attention to his nephew's case. "Justice has no border," he said. "It affects every one of us."