WWW- If the U.S. Justice Department is successful in obtaining a week’s worth of search terms from Google, which it demanded as part of an attempt to defend a 1998 Internet pornography law, a second round of subpoenas is shaping up to be far more intrusive.

The American Civil Liberties Union warned Friday that if the first subpoena is granted–giving the government’s expert the information to use to evaluate the effectiveness of porn filters–the ACLU’s legal assault on the same antipornography law will require it to target Google as well.

“If the government utilizes the information in any manner, we’re very likely going to need to do follow-up discovery,” ACLU attorney Aden Fine said.

A legal brief the ACLU filed with a federal judge in San Jose, Calif., on Friday says its request would seek to learn how Google’s search engines operate, how Google serves up links in response to queries and whether there is “any way to distinguish between queries generated by actual individuals and queries generated by artificial programs or software.”

The civil liberties group, which characterizes itself as a staunch defender of privacy, says it is not eager to expose details about Google’s inner workings and the habits of its users. The ACLU says it has “no need or desire to obtain any of this information from Google.” But, the group warns, if the government gets the information, it would have little choice.

The unexpected news of a second subpoena from the ACLU could complicate the Justice Department’s attempt to convince U.S. District Judge James Ware to grant its request. Ware has scheduled a hearing for March 13.

The Justice Department is seeking a random sample of 1 million Web pages from Google’s index, along with copies of a week’s worth of search terms to aid in the defense of the Child Online Protection Act (COPA). America Online, Microsoft and Yahoo voluntarily complied with similar requests.

A representative for the Justice Department did not immediately respond to requests for comment Friday.

For its part, Google has raised the possibility of being enmeshed in the increasingly complex COPA lawsuit as a reason to oppose the subpoena. That would place Google “in the witness chair, and exposes Google’s intellectual property to cross-examination in open court by the ACLU, its counsel, experts and consultants,” the company said in its own brief filed Friday.

AOL, Microsoft and Yahoo each have received two subpoenas from the Justice Department, one asking for information about filtering technology and the other asking for search terms. The ACLU has given AOL a subpoena to appear at a deposition “asking for testimony about their parental control technology,” according to the ACLU’s Fine.

The Justice Department has disclosed nothing about what it plans to do with the records from search companies, except to say it has hired Philip Stark, a professor of statistics at the University of California at Berkeley, to evaluate the search logs.