Here's why this court ruling might put an end, once and for all, to a big Republican talking point about Russian 'collusion'

One of the most common defenses of President Donald Trump and his associates as Special Counsel Robert Mueller's investigation has heated up is that "collusion" is not a crime, even if Mueller can prove that it took place. It's a favorite claim of Trump and Rudy Giuliani.

To some degree, this is just wordplay. There is no federal statute that explicitly defines "collusion" or makes it a crime, so of course that would not be literally spelled out on any of the Mueller team's dozens of indictments, convictions, and plea agreements with U.S. and Russian suspects.

But insofar as "collusion" — if that is taken to mean Russian actors working together to break U.S. laws — is in fact a crime, Mueller is absolutely hot on its trail. And a federal court decision last week reveals just how close the investigation is to actually proving such a thing took place.

In the decision, D.C. District Judge Dabney Friedrich, a Trump appointee, ruled Mueller can proceed with indictments against Concord Management and Consulting, a Russian company accused of helping manage a "troll farm" that used social media to broadcast election propaganda to the United States.

Specifically, Mueller sought to charge Concord, and several other Russian individuals, with 18 U.S.C. § 371, or conspiracy to defraud the United States. Prosecutors say that by secretly funding and promoting targeted messages to influence the election outside of any proper channel, the defendants conspired to stop the Federal Election Commission from enforcing campaign finance law, the Justice Department from registering them as foreign agents, and the State Department because they lied on visa applications to travel to the United States.

At issue in this ruling was whether Mueller could bring these charges alone, since the indictment did not charge any of the Russian companies or individuals with the underlying violations of the laws they allegedly conspired to defeat (failure to register as a foreign agent, for example, or failure to report campaign activity to the FEC). Concord argued to Friedrich that the conspiracy charge could not stand on its own, because "there is no such crime as interfering with an election."

Friedrich did not agree. She denied Concord's request to dismiss the charges, noting that established law does not require prosecutors to prove any underlying crime to bring a charge of conspiracy. In other words, she held that a conspiracy to interfere with U.S. elections can itself be a crime — and effectively laid out a way for Mueller to prosecute Russian actors over "collusion."

Between this ruling and the fact that there are clear lines of evidence of involvement between Russia and the Trump campaign, it is getting untenable to claim that collusion isn't a crime — or that the effort to uncover it will not take members of Trump's inner circle down with it.