Ward filed a motion earlier this month asking U.S. District Judge Vaughn Walker to allow him to argue he had "a legitimate, journalistic purpose" for his actions because he was doing research for a book.
Ward, 56, a former host on KGO radio in San Francisco, is accused of three counts of receiving child pornography, knowingly distributing it and attempting to distribute it in December 2004 and January 2005.
The case is tentatively scheduled for trial in July and a pretrial hearing on the motion is tentatively set for June 12.
Ward, the author of several previous books and articles, says in the court filing that he came into possession of the illegal photographs while doing research for a new book. Defense attorney Doron Weinberg has previously said the book was about hypocrisy.
Ward contends he should be allowed to argue the research was protected by the constitutional First Amendment right to free speech.
Weinberg wrote, "If given the chance at trial, Mr. Ward will offer proof that he received and distributed the contraband exclusively for the purpose of furthering his research, and that he intended to destroy the material upon completion of his journalistic enterprise."
Prosecutors from the U.S. Justice Department's child exploitation and obscenity section opposed the motion in a response filed on Thursday. The prosecutors wrote, "The law provides no First Amendment-based license to journalists to violate laws."
The federal lawyers argued that allowing Ward to present a free-speech defense "would invite every defendant charged with child pornography crimes to suddenly become a legitimate researcher educating the masses via their Web blog."
Ward, a former Catholic priest who is married and has four children, previously hosted a nighttime 10 p.m. to 1 a.m. show Monday through Friday and a Sunday morning show called Godtalk on KGO.
He was charged in an indictment that was issued under seal in September and unsealed on Dec. 7, the day after he pleaded not guilty to the charges.