In the beginning, people thought of it as a domestic quarrel, one of those unseemly squabbles that families get into and the law stays out of. But in the last half-dozen years, we have come to regard child-snatching as a peculiarly malevolent kid of child abuse.

In one case history after another, we learned about parents who put their children through physical danger and emotional devastation in order to "grab" them. We learned about parents who never returned their children from a "visit," parents who carried them from the school playground or had them nabbed by hired men in the back yard. As many as 100,000 a year take their kids and run, hiding out, living from motel to motel, moving from state to state.

We also learned how often the child-snatchers succeeded, and how the legal system "helped" them. If a father won custody in one state, a mother could still win it in another state. It was possible for a child-snatcher to go judge-shopping, state-shopping; it was possible for a child to "belong" to his mother in Pennsylvania and to his father in Massachusetts.

The victims were not only the left-behind parents but the children.

Finally, in the eleventh hour of this lame-duck Congress, the president used his good right hand to sign the first federal bill to deter child-snatching.

When the law goes into effect in July, it will no longer be possible for a parent who has lost in one court to go shopping for legal custody in another Haven" state. Each state in the union must recognize the prior custody ruling of another state.

At the same time, a victim parent will be able to use the fedral Parent Locator Service to help find a missing child. The PLS, the only national program that can trace people through their Social Security numbers, is already being used to find men who have run out on child-support payments. Now, as Arnold Miller, the head of Children's Rights, Inc., says, "We can use its power not only to bring back the dollar, but the child."

Lastly, the passage of his bill also means that the FBI can be called on to locate a child abducted by his own parent. In the 38 states where child-snatching is a felony, the state can issue a warrant to the FBI.

This bill has been six years in the writing, lobbying, compromising. It took the persistence of victim parents like Miller and supporters like Patty Hoff, former minority counsel on the Senate Judiciary Committee and staffer to Sen. Malcolm Wallop (R-Wyo.), to overcome resistance and apathy.

In the end, these advocates got a great deal, but not everything they wanted. Because of resistance in Congress and especially in the FBI, child-snatching is still not a federal crime.

Without that clause, it's hard to know exactly how effective this first national la will be in the real world for the real parent trying to get a child back. The bill may do more to locate children than to return them.

The enforcement procedure depends on the states. Inasmuch as 55 percent of children are abducted before the custody case even goes to court, it is still possible for a parent to abduct a child and get the first decree in another state.

The role of the Parent Locator Service is unclear. No one knows what the responsibility of the PLS will be after it has found the child. Simply to notify the parent left behind? To make sure the abducting parent doesn't takk off again?

The role of the FBI is also somewhat vague. No one can yet say how or how much the FBI will get involved in enforcement. Under this bill, a state has to issue a felong warrant for the arrest of the parent to the FBI. So far, says Miller, only six actually issue warrants.

Finally, the federal law does nothing for those children who have been kidnapped out of the country. That problem awaits the completion of the international treaty.

Despite all these limitations, the new law can work as a powerful deterrent. At last, the system no longer encourages child-snatching; it forbids it. We have the first federal recognition that a child-snatcher is not merely some overwrought, caring parent, but a fugitive and destructive kidnapper.