The image was riveting, as justice John Paul Stevens, a Chicago native, presented it. A ga

ng member and his father are hanging out near Wrigley Field. Are they there "to rob an unsuspecting fan or just to get a glimpse of Sammy Sosa leaving the ball park？" A police officer has no idea, but under Chicagos anti-gang law, the cop must order them to disperse. With Stevens writing for a 6-to-3 majority, the Supreme Court last week struck down Chicagos sweeping statute, which had sparked 42,000 arrests in its three years of enforcement. The decision was a blow to advocates of get-tough crime policies. But in a widely noted concurring opinion, Justice Sandra Day OConnor suggested that a less draconian approach-—distinguishing gang members from innocent bystanders—might pass constitutional muster. New language could target loiterers "with no apparent purpose other than to establish control over identifiable areas, to intimidate others from entering those areas or to conceal illegal activities," she wrote. Chicago officials vowed to draft a new measure. "We will go back and correct it and then move forward," said Mayor Richard Daley. Chicago officials, along with the League of Cities and 31 states that sided with them in court, might do well to look at one state where anti-gang loitering prosecutions have withstood constitutional challenges; California. The state has two anti-loitering statutes on the books, aimed at people intending to commit specific crimes—prostitution and drug dealing. In addition, a number of local prosecutors are waging war against gangs by an innovative use of the public-nuisance laws. In cities such as Los Angeles and San Jose, prosecutors have sought injunctions against groups of people suspected of gang activity. "The officers in the streets know the gang members and gather physical evidence for lengthy court hearings," says Los Angeles prosecutor Martin Vranicar. If the evidence is enough to convince a judge, an injunction is issued to prohibit specific behavior—such as carrying cell phones or pagers or blocking sidewalk passage—in defined geographical areas. "It works instantly," says San Jose city attorney Joan Gallo, who successfully defended the tactic before the California Supreme Court. "A few days after the injunctions, children are playing on streets where they never were before. " So far, only a few hundred gang members have been targeted, out of an estimated 150,000 in Los Angeles alone. But experts say last weeks decision set the parameters for sharper measures. Says Harvard law professor Laurence Tribe: "It just means they have to use a scalpel rather than an invisible mallet. "

What does the author intend to illustrate with the example of the gang member and his father？

A．How the anti-loitering law works.

B．How to maintain charming image.

C．How tough the crime policies were.

D．Why Chicago"s sweeping statute stroke down.