NEW YORK - A pregnant teenager dependent on her library's Internet terminals is apt to find some sites that discuss abortion blocked now that the Supreme Court has endorsed software filters for computers at public libraries.
Or perhaps a student is researching gay rights for a high school assignment. He has no computer at home, and the ones at his school and library block many sites on the topic. He turns in an incomplete report.
Monday's decision to uphold filtering requirements in libraries could hurt efforts to equalize access to the Internet among Americans.
Minorities and low-income Americans, who are more likely to log on solely at libraries, could face an incomplete Internet because of filters that block out material on abortion, gay rights and a host of other topics besides porn.
"It is yet another obstacle for low-income Americans to having the same kind of access and the same kind of information resources and awareness that their more well-to-do peers have," said Andy Carvin, senior associate at the Benton Foundation, a Washington, D.C., organization that studies Internet access.
Under the law the high court affirmed, libraries must block pornography to receive certain federal technology grants.
But the available software filters make mistakes and often block legitimate sites. House Majority Leader Dick Armey is among owners of Web sites that, though lacking anything pornographic, have at one time been filtered out.
Many librarians plan to reject federal funding to keep unfiltered access, but poorer communities cannot afford to do so, said Judith Klug of the American Library Association. And those communities, she said, are where Americans most depend on libraries for Internet access.
According to the Commerce Department, 10 percent of Internet users get access through a library. Blacks and Hispanics are more likely than whites and Asians to be in that group.
And while 13 percent of white library users have no other access at home, work or school, 16 percent of Hispanics and 19 percent of blacks have a similar dependence on libraries.
The Commerce report, from February 2002, also found that the lower the household income, the more likely a person is to depend on the library for Internet access.
Klug said the filtering law puts librarians in "a position of punishing people who are poor."
Vendors of filtering software acknowledge the flaws, but they say librarians can unblock filters upon request - a right the Supreme Court affirmed, at least for adult patrons. Susan Getgood, senior vice president at SurfControl Inc., said filters are merely tools for implementing policies the libraries develop themselves.
David Miller, a spokesman for Family Friendly Libraries in Cincinnati, said Internet searches typically return "more material than any one person can read," so there's no harm even if an occasional site gets mistakenly blocked.
A study from the Kaiser Family Foundation, a nonprofit research organization on health care, found that at the least-aggressive levels, filtering software blocked only 1 percent of health sites surveyed and 9 percent of sites specifically on sexual health.
Some library patrons say they don't mind asking a librarian to unblock sites when mistakes are made. Del Hewitt, 28, understands the objectives.
"If you want to look at porn, you should go somewhere else," Hewitt said, logging on at lunch time from a terminal at Atlanta-Fulton Public Library. "This isn't the place to do it."
But "it would be embarrassing to have to go up and tell them what you're looking at, even if it is for research purposes," said Wanda Lugo, 31, who lives in a lower-income Boston neighborhood and has no other Internet access.
Library officials say unblocking sites would be labor intensive and divert their computing staffs from such tasks as teaching senior citizens how to get online and children how to research.
And patrons may not even know that information is being blocked and thus would not know to ask - a point noted by Justice John Paul Stevens in his dissent.
Furthermore, both the law and the high court ruling are silent on when, if ever, librarians may disable filters for minors.
Nonetheless, the law could have one bright spot for bridging the digital divide, said Stefaan Verhulst, chief of research at the Markle Foundation, which studies policies on information technology.
"The counter argument might be that filtering might increase the confidence among parents," he said, making them more willing to send kids to library computers unsupervised.