WASHINGTON – Thomas Lambert made no attempt to hide the kind of videos he peddled from his Montana home – hard-core sex tapes involving bestiality, sadomasochism and simulated rape.

The 65-year-old former schoolteacher had little reason to believe he could get in trouble. He was selling tapes to adults who wanted them and there had not been a federal obscenity prosecution in Montana in at least 16 years, according to his lawyer, Mark Errebo.

But Lambert and co-defendant Sanford Wasserman were charged last spring with violating federal obscenity statutes. In pleading guilty, they joined a growing number of purveyors of pornography whom the Bush administration has pursued.

Since 2001, 40 people and businesses have been convicted and 20 additional indictments are pending, said Andrew Oosterbaan, chief of the Justice Department’s child exploitation and obscenity section. By comparison, there were four such prosecutions during the eight years of the Clinton administration, he said.

Attorney General Alberto Gonzales, like his immediate predecessor, John Ashcroft, has pledged to make obscenity prosecutions a priority. The department is expected to announce soon the creation of a special unit within its criminal division to focus on adult obscenity cases.

“Enforcement is absolutely necessary if we are going to protect citizens from unwanted exposure to obscene materials,” Gonzales recently told federal prosecutors. He directed U.S. attorneys to report back by late July on effective ways to crack down on obscenity and what tools the prosecutors might need.

Those kind of words please religious conservatives, who claim the Clinton administration virtually ignored the proliferation of pornography, particularly on the Internet, during the 1990s.

Critics say a few dozen criminal cases will not dent an industry with an estimated $10 billion a year in sales. Moreover, they say, the effort is an assault on the First Amendment protection of speech and expression, however distasteful.

“They’ll find some sacrificial victims, but the porn industry will go on,” said Marjorie Heins, founder of the Free Expression Policy Project at New York University’s Brennan Center for Justice.

A proponent of strict enforcement of obscenity laws agreed with Heins that so far, the administration has aimed mostly at minor figures in the industry.

“At some point, they’re going to have to ratchet it up if they want to do something meaningful,” said Robert Peters, president of Morality in Media.

Oosterbaan said the government has won convictions in high-profile cases. He cited a guilty plea last year from John Coil of Highland Village, Texas, who owned and operated 27 adult-oriented businesses in Texas, New Mexico and Arizona. Coil forfeited an estimated $8.1 million in property to the government and was sentenced to more than five years in prison.

In addition, there is the 23-count indictment against Edward Wedelstedt of Littleton, Colo., and his Goalie Entertainment Holdings Inc. Wedelstedt owns pornographic bookstores in 18 states; the indictment lists six allegedly obscene videos and DVDs.

The government is seeking the forfeiture of millions of dollars in real estate and other property, including a Lear jet, in the Wedelstedt case.

Henry W. Asbill of Washington, Wedelstedt’s lawyer, said the indictment was politically motivated.

“My client supplies his own stores with adult materials that are for adults only. Consenting adults come into the stores and view or rent or buy the movies,” Asbill said.

In trying to prosecute obscenity, it long has been difficult to distinguish obscenity from indecent content. As former Supreme Court Justice Potter Stewart once famously said about hard-core pornography, “I know it when I see it.”

The Supreme Court has ruled that many dirty pictures are constitutionally protected free speech that adults have the right to see and buy. The high court also has rebuffed Congress’ attempts to ban or restrict adult-oriented Web sites.

But the court also set out ground rules for obscenity in its landmark 1973 ruling in Miller v. California that allow the standards for offending material to vary from one community to the next.

The Justice Department’s approach has been to identify videos that even some in the pornography business find unappealing and to bring charges in more socially conservatives places, where possible.

In the Montana case, Lambert distributed videos that even his lawyer said were “frankly, disgusting.”

In the case against Wedelstedt, the government filed charges in Dallas, where the Colorado resident was indicted.

But a recent court decision in Pittsburgh could upset the administration’s plans. U.S. District Judge Gary Lancaster tossed out an obscenity indictment against Extreme Associates Inc. and its owners, Robert Zicari, and his wife, Janet Romano, both of Northridge, Calif.

Lancaster ruled that prosecutors overstepped their bounds while trying to block the company’s hard-core movies from children and from adults who did not want to see such material. He said the company can market and distribute its materials because people have a right to view them in the privacy of their own homes.