A federal judge barred a journalist from invoking the First Amendment during his trial on charges of sending and receiving online child pornography.

Larry Matthews, a veteran reporter who now works for National Public Radio, has said he was researching the explosion of child porn on the Internet and the efforts of authorities to curb it.He had planned to argue during his trial beginning Tuesday that he has a right to view such materials under the amendment, which guarantees freedom of speech and the press.

U.S. District Judge Alexander Williams Jr. knocked down Matthews' central defense on Monday, agreeing with prosecutors that intent is irrelevant under federal law. He said Matthews could have interviewed authorities and looked up child pornography prosecutions for his research.

"The law is clear that a press pass is not a license to break the law," the judge wrote.