The Supreme Court, acting in the case of a Wisconsin toddler who was severely beaten by his father, ruled 6-3 Monday a state has no constitutional duty to protect children from abusive parents.

In an opinion by Chief Justice William Rehnquist, the high court said county welfare officials in Wisconsin could not be sued for violating the rights of Joshua DeShaney, a 4-year-old boy who suffered permanent brain damage in a beating administered by his father, Randy DeShaney.Although conceding "the facts of this case are undeniably tragic," the court concluded that "nothing in the language" of the Constitution "requires the state to protect the life, liberty and property of its citizens by private actors."

DeShaney, now 9, has been institutionalized since March 8, 1984, when his father beat him into a coma, leaving him permanently paralyzed and profoundly retarded. The beating followed almost two years of abuse during which time the Winnebago County Department of Social Services monitored the case, but took no action.

Following the beating, Joshua and his mother, Melody DeShaney, sued the county for damages, claiming that its failure to protect the child deprived him of liberty in violation of his civil rights.

The nationally publicized child abuse story took the court into a previously unexplored area of the 14th Amendment, which states that no person shall be deprived of life, liberty or property without "due process of law."

A district court and the 7th U.S. Circuit Court of Appeals both ruled that the 14th Amendment did not require county officials to protect the child from his father.

The high court agreed, saying, "Judges and lawyers, like other hu-mans, are moved by natural sympathy in a case like this to find a way for Joshua and his mother to receive adequate compensation for the grievous harm inflicted upon them.

"But before yielding to that impulse, it is well to remember once again that the harm was inflicted not by the state of Wisconsin, but by Joshua's father."

Justices William Brennan, Thur-good Marshall and Harry Blackmun dissented from the ruling, contending that the county did have a constitutional obligation to protect Joshua once it learned of his father's abusive conduct.

Echoing comments he made when the case was argued, Blackmun wrote, "Poor Joshua! Victim of repeated attacks by an irresponsible, cowardly and intemperate father, and abandoned by respondents (the county) who placed him in a dangerous predicament and who knew or learned what was going on, and yet did essentially nothing except, as the court revealingly observes, `dutifully recorded these incidents in their files.' "