As the Interim Study Commission on Immigration Issues continues its work in Indianapolis, there's a very important question the legislators should be asking: Why are we here?

At Tuesday's meeting, much of the time was spent trying to calculate the costs of illegal immigrants on a variety of government services, ranging the gamut from schools to health care to prisons.

There are few firm numbers.

The Indiana Department of Correction said it had 504 foreign-born prisoners who weren't U.S. citizens. Incarcerating them will cost the state about $9.8 million this year. But how many arrived legally? The agency doesn't know.

The Family and Social Services Administration spends about $5 million a year in Medicaid coverage for pregnancies and illegal immigrants who can't afford care.

That's about as definite as it gets. Illegal immigrants, after all, are under the radar, so no one even knows how many there are in Indiana.

The Washington, D.C.-based Pew Hispanic Center estimates Indiana has 100,000 undocumented people -- not necessarily illegal immigrants -- but there's a wide margin for error.

The bigger question, however, is what the state's role should be in the debate on illegal immigration.

The U.S. Supreme Court is considering conflicting federal court decisions on immigration policy in Arizona, Missouri and Pennsylvania.

Bernard Trujillo, a Valparaiso University law professor, advised the study commission to bide its time: "Why jump on the bandwagon until you know whether the bandwagon is about to jump off a cliff?"

Let the U.S. Supreme Court rule on what states may do about immigration before Indiana jumps in on what is, and should be, a federal issue anyway.

Last weekend, federal agents arrested 144 illegal immigrants in a series of sweeps in the Chicago area and northern Indiana. The federal government isn't ignoring its responsibility.

The Indiana General Assembly should be very reluctant to take on this issue.

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