CNN  — 

A federal judge is allowing a major January 6 conspiracy case against four Proud Boys leaders to move forward, rejecting their bid to throw out the charges.

Judge Timothy Kelly, in a 43-page opinion issued Tuesday, sided with the Justice Department on several key legal questions, giving momentum to prosecutors as they prepare for the first wave of US Capitol riot-related trials beginning in February.

Kelly greenlit prosecutors’ use of a felony obstruction charge, among several other charges, against Proud Boys leaders Ethan Nordean, Joseph Biggs, Charles Donohoe and Zachary Rehl. (They have all pleaded not guilty.) The judge also rejected the defendants’ claims that the riot could have been a protected First Amendment demonstration.

“No matter Defendants political motivations or any political message they wished to express, this alleged conduct is simply not protected by the First Amendment,” Kelly wrote.

“Defendants are not, as they argue, charged with anything like burning flags, wearing black armbands, or participating in mere sit-ins or protests,” Kelly added. “Moreover, even if the charged conduct had some expressive aspect, it lost whatever First Amendment protection it may have had.”

Kelly also wrote: “Quite obviously, there were many avenues for Defendants to express their opinions about the 2020 presidential election, or their views about how Congress should perform its constitutional duties on January 6, without resorting to the conduct with which they have been charged.”

The felony obstruction charge, which carries a maximum 20-year prison term, has been the cornerstone of many of the Justice Department’s most serious cases related to the January 6 attack on Congress. Nearly every defendant charged with it is challenging its legality in court.

Kelly, an appointee of former President Donald Trump, became the fourth DC District Court judge to uphold prosecutors’ use of the law in the January 6 cases. A fifth judge, Randolph Moss, also signed off on the Justice Department’s use of the charge in January 6 riot cases in yet another ruling on Tuesday night.

The ruling in the Proud Boys case is especially notable because it and a separate case against members of another right-wing group, the Oath Keepers, are two of the most prominent prosecutions related to January 6. (Judge Amit Mehta previously upheld prosecutors’ use of the obstruction charge in the Oath Keepers case. Judges Dabney Friedrich and James Boasberg also have taken the same position in other January 6 cases.)

Members from both groups are charged with conspiracy. In this Proud Boys case, the four leaders are accused of working together to lead and outfit members of their group in a paramilitary-style, violent assault on the Capitol.

This story has been updated with further developments Tuesday.