WASHINGTON — Judge Richard J. Leon, who shook up Washington on Monday by declaring a National Security Agency data collection program “almost Orwellian,” is a conservative and a vivid writer who does not shrink from criticizing the federal government on matters as varied as pornography, death penalty drugs and terrorism suspects at Guantánamo Bay, Cuba.

With his use of exclamation points (“How utterly disappointing!” he once wrote, excoriating the Food and Drug Administration) and cultural references (he mentioned the Beatles and Ringo Starr in a footnote in Monday’s ruling), Judge Leon does not seem bound by judicial sobriety.

“He’s very passionate; he uses a lot of italics and exclamation points,” Orin S. Kerr, a professor at the George Washington University Law School and a defender of the N.S.A.’s surveillance programs said referring to the way Judge Leon wrote the decision. Mr. Kerr said he found the judge’s ruling short “on legal reasoning.”

Judge Leon, 64, a Republican nominated on Sept. 10, 2001, by President George W. Bush and confirmed in 2002, has backed the government in past cases. He did so in 2005, holding that detainees at Guantánamo had no right to due process (though he later ordered the release of some).