U.S. immigration law is like art. Everybody can tell you what's wrong with the work at hand; few can do it better.

We can't even agree on what should be the primary emphasis of our immigration law: U.S. self-interest or charity; population control and skills recruitment at home, or relief from the pressures of population, hunger and political oppression abroad. We agree that it ought to be fair, but we will argue endlessly over what that means.

The omnibus immigration bill introduced last week by Sen. Alan Simpson (R- Wyo.) and Rep. Romano Mazzoli (D-Ky.) is hardly a work of art, though it does confront some of the toughest issues: the need for setting realistic limits on the number of immigrants without repealing the invitation of the Statue of Liberty; the need for controlling illegal entry without turning America into a police state; the need for fairness in choosing among those who would come to this country.

Perhaps the most troublesome areas of the bipartisan proposal are the problem of identifying those who may be illegal immigrants, which has generated a fair amount of comment, and the problem of Amerasians, which hasn't.

Rep. Stewart McKinney (R-Conn.) has been agonizing over the Amerasian question for a few years now, ever since he saw firsthand the heart-rending treatment of the children of Asian women and American GIs. He says that Simpson and Mazzoli have "totally missed the point" he has been trying to make: that the Amerasians are our children, and ought to be allowed to come here without restriction, so long as they can find sponsors here.

The Amerasian section of the Simpson- Mazzoli bill is essentially an adoption proposal. It would admit applicants between the ages of 14 and 21, provided: 1) they apply within two years of enactment of the bill; 2) they can prove their fathers are American military men who served in Korea, Vietnam, Cambodia or Laos; 3) they are "subject to significant discrimination in the country of residence because of such parentage; 4) they are coming to the United States to be adopted. Even then, the maximum to be admitted would be 10,000--2,000 a year for five years.

McKinney finds nearly all the qualifications troublesome. The age limit and the requirement that the would-be immigrants apply within two years ignores the fact that American GIs are still fathering babies in Asia, he said. The requirement that they be adopted before they come here is unnecessarily burdensome, he contends, pointing out that such adoptions would have to be arranged through Asian agencies. It can cost between $7,000 and $9,000 to place a child for adoption in Korea, he said, while the same child could be adopted here for a fraction of that sum.

McKinney particularly objects to the limit of 10,000 immigrants over five years. No one knows how many Amerasian children there are, but estimates begin at 30,000 and run to five times that number.

"These are our children," he said when he introduced his own proposal last summer. "They have been left to a future of little or no opportunity for education or jobs. Probably even worse, they have been abandoned in a society that does not recognize them as people . . . that does not look at them as they walk down the street, unless it is to call them dirty names. And their only sin is that they have U.S. fathers."

Nor, he noted the other day, is the problem solely one of unfortunate history. "American GIs are still producing kids in Asia," he said. "I'm told that we even have buses that pick up soldiers at their bases and take them to approved 'hot spots' where the women are supposed to be clean."

The crucial point, he says, is recognition of these children as Americans. "They can enter under existing law if we would only admit that they are our kids. There's no purpose in creating a special immigration class for a few of these kids, admitting that we have produced 10,000 of them--if they happen to be the right ages." His own bill, for which he has 180 cosponsors, would require only that prospective Amerasian immigrants have U.S. sponsors who would guarantee their support at no less than 125 percent of the official poverty level.

It may not be art, but I like it.