U.S. District Court Judge Marilyn Hall Patel, in a decision released Tuesday, denied a motion by Justice Department attorneys to dismiss the suit brought by former University of California, Berkeley, graduate student Daniel J. Bernstein last year.
Attorneys for the government had argued that the computer source code for Bernstein's program is not protected by the First Amendment because it is a tool used to encrypt messages rather than a language used to express them.
Patel sharply disagreed. ''This court can find no meaningful difference between computer language ... and German or French,'' she wrote. ''Contrary to the defendant's suggestion, the functionality of a language does not make it any less like speech.''
The judge added: ''Like music and mathematical equations, computer language is just that, language, and it communicates information either to a computer or to those who can read it.'' She also cited a recent federal appeals court ruling that said use of a foreign language was an exercise of free speech.
Although the government, when protecting the national security, can regulate conduct in ways that may incidentally restrict speech, the judge said, its export regulations for cryptography ''may reach farther than is justifiable.''
Cindy Cohn, the attorney representing Bernstein, said the ruling ''means the government has to meet the First Amendment test in order to regulate encryption software.'' She said such software will be important to the development of commerce on the Internet.
Justice Department lawyer Anthony Coppolino, who defended the State Department restrictions in court, could not be reached for comment. But in arguments before Patel in October, he said a code whose sole function was to create secrecy was not entitled to constitutional protection.
''We just don't think that a functioning commodity that can maintain confidentiality is speech,'' Coppolino told the judge. He said the encoded message ''could be a love letter, or it could be a communication from Saddam to bomb Kuwait.''
Federal law enforcement agencies are also concerned about losing their ability to wiretap, said Michael Froomkin, a law professor at the University of Miami. He said encryption would be quickly incorporated into the worldwide software market if Bernstein won his case.
Bernstein, now at the University of Chicago, developed his encryption program, Snuffle, and a decryption program, Unsnuffle, while a graduate student at UC- Berkeley. Snuffle converts a readable message into a code that can be read only by using Unsnuffle.
The State Department initially decided, in 1993, that not only the programs but also an academic paper written by Bernstein to describe his ideas were military articles that required licenses to communicate abroad. The department withdrew that designation for the academic paper in 1995 but left it in place for the programs, prompting the lawsuit.
The suit contends State Department regulations classifying cryptographic systems as munitions are content-based, overly broad restrictions on speech and prior restraints on publication. Patel did not decide any of those issues but ruled that they would be determined under the standards of free speech.
Last month a judge in Washington tossed out a similar case filed by the author of a book on cryptography. In that case, the State Department allowed Bruce Schneier to export copies of his book, which contained the source code for several cryptographic programs, but refused to let him export computer disks containing the same programs.