WASHINGTON – California’s policy of granting lower, in-state tuition to illegal immigrants who graduate from its high schools is facing a challenge in the Supreme Court from those who say it violates federal immigration law.

At issue is a little-known provision in a 1996 law that bars states from giving “any postsecondary benefit” to an “alien who is not lawfully present in the United States … on the basis of residence within a state.”

Last year, in the first ruling of its kind, the state supreme court upheld California’s policy and said it did not conflict with federal law.

The justices may announce as soon as Monday whether they will hear the challenge or dismiss it. The justices may turn it away because there is no dispute amongst the lower courts. It is also possible the high court could ask the Obama administration for its view before deciding.

If the high court were to hear the case and overrule California, the decision would affect 11 other states — Illinois, Kansas, Maryland, Nebraska, New Mexico, New York, Oklahoma, Texas, Utah, Washington and Wisconsin — which have opted to give in-state tuition to students who are illegal immigrants.

Another 12 states have explicitly refused to grant in-state tuition to illegal immigrants. For its part, the federal government — through the Clinton, Bush and Obama administrations — has taken no steps to enforce the measure.

Citing this confusion, the Washington-based Immigration Reform Law Institute appealed the California case to the Supreme Court. Kris W. Kobach, a lawyer for the institute who led efforts in Arizona and elsewhere to tighten laws against illegal immigrants, estimated California “spends in excess of $208 million a year subsidizing the tuition of illegal immigrants.”

The federal law forbids giving “preferential treatment” to illegal aliens “on the basis of residence” within their state. The California law, by contrast, says students may qualify for in-state tuition based on “high school attendance in California for three or more years and graduation from a California high school.”

The state’s lawyers argue that since the benefit turns on high school attendance, not “residence,” it does not violate federal law.

In 2009, the 10-campus University of California system said 2,019 students paid in-state tuition under the terms of the state law. Of these, about 600 were believed to be illegal immigrants.