(WASHINGTON) -- The Supreme Court said Monday it will decide whether cities can prohibit more than one adult business from operating on the same site. In the same sitting, the court turned away other free-speech cases.

Two Los Angeles adult bookstore operators, already restricted from operating too close to similar businesses, said it is unfair to bar them also from diversifying an existing business.

Free speech defenders also say piling zoning restrictions onto adult businesses amounts to nothing more than trying to shut them down.

These other free speech cases were up Monday:

-The justices turned away appeals dealing with the Ku Klux Klan's participation in a highway cleanup campaign and a student barred from giving a valedictory address that talked about Jesus.

-The court also ruled unanimously that Indian tribes do not qualify for exemptions on releases of documents under the Freedom of Information Act.

In the Klan case, Missouri lost a bid to ban the organization from its Adopt-A-Highway cleanup program. The court, without comment, turned down the state's argument that it should be allowed to bar the Klan from the litter control program because the organization won't accept blacks and other minorities as members.

``It's what I expected right from the beginning,'' said Thomas Robb, national director of the Ku Klux Klan in Harrison, Ark. ``With us it was purely a constitutional issue.''

Missouri's lawyers had said the state has a right to control its own speech and that allowing the Klan to participate would violate the 1964 Civil Rights Act's ban on racial discrimination in federally funded programs.

Also without comment, the court turned down an appeal from a California high school valedictorian barred from giving a graduation speech in which he had planned to ask the audience to ``accept God's love'' and to live by ``Jesus' example.''

The bookstore case builds on the court's previous rulings that local governments may pass restrictive zoning laws intended to prevent the development of red light districts.

In Los Angeles, adult-oriented businesses such as X-rated movie houses, sex toy shops and adult bookstores may not operate within 1,000 feet of one another, nor within 500 feet of a church, school, park or residential neighborhood.

In passing those 1978 rules, the city cited a study charting harmful effects of concentrations of adult businesses, including higher crime and lower property values.

In 1983, the city refined its rules to prohibit multiple adult businesses from operating in the same building.

``This issue is, did we want the adult entertainment mall?'' said Claudia McGee Henry, senior assistant city attorney in Los Angeles. ``It was never the city's intent to disperse adult businesses, but then allow a mall with as many businesses as you can cram in there.''

Two adult bookstores with separate video viewing stations later challenged the 1983 rule as an unconstitutional limit on free expression. The 9th U.S. Circuit Court of Appeals (news - web sites) eventually ruled that the city did not provide enough evidence of the potential harm from having multiple businesses on a single site.

Los Angeles has a ``substantial government interest'' in reducing crime in its neighborhoods, but it did not provide enough evidence that the restriction would serve that goal, the appeals court said.

The city's lawyers said a 1984 Supreme Court ruling ``does not require a city council to independently investigate or corroborate each potential problem when it acts in furtherance of the public interest.''

The bookstores' lawyers said a zoning law like the Los Angeles ordinance ``would allow the absolute destruction of any adult bookstore business'' by defining each type of product as a separate business that could not occur in the same store.

A Supreme Court decision in the case is expected to clarify what justification a local government needs for the multiple-business ban - or whether such a rule cannot be justified.

``I think we are seeing cities and counties around the country continuously stretching the rationale for imposing zoning restrictions on adult businesses, and this case is about as much of a stretch as you can have,'' said Steven Shapiro, legal director for the American Civil Liberties Union (news - web sites), which has fought restrictions on adult bookstores in the past.

Using a broad definition of speech - here titillating or pornographic books and videos - the ACLU says that Los Angeles wrongly seeks zoning rules that treat sexual speech differently from other kinds of speech.

``At some point this becomes thinly veiled subterfuge'' to put adult bookstores out of business, Shapiro said.

The cases are Los Angeles v. Alameda Books, 00-799; Yarnell v. Cuffley, 00-289; Niemeyer v. Oroville Union High School District, 00-1074; and U.S. Department of Interior v. Klamath Water Users Protective Association, 99-1871.