Rep. Justin Amash’s statement that President Trump has met the threshold for impeachment was obviously a setback for Trump, given that there is now a congressional Republican saying Trump’s actions went too far. But it was also a stated rebuke of Attorney General William P. Barr and his actions in pre- and post-spinning the results of the Mueller report.

And after getting blowback from fellow Republicans — and a pro-Trump primary challenger in his Michigan district — Amash isn’t backing down. On Monday, he expanded on his case against Barr and those echoing Barr’s defense of Trump. In doing so, he raises some important points.

Let’s walk through his Twitter thread.

Ding ding. This is a case Barr has made from the moment he started characterizing the Mueller report. And from that moment, legal experts have questioned his focus on this particular defense of Trump.

“In making this determination” that Trump would not be accused of obstructing justice, Barr wrote in his initial letter summarizing the principal conclusions of the Mueller report, “we noted that the Special Counsel recognized that ‘the evidence does not establish that the President was involved in an underlying crime related to Russian election interference,’ and that, while not determinative, the absence of such evidence bears upon the President’s intent with respect to obstruction.”

Barr would also refer to the lack of an underlying crime in his news conference before the Mueller report was released and in his later congressional testimony. While perhaps not “determinative,” it’s clear he’s arguing that this is important.

But while Mueller decided there was not enough evidence to support an accusation of conspiring or coordinating with Russia, there are in fact underlying crimes that Trump clearly had an interest in obscuring, as evidenced by his campaign chairman Paul Manafort’s convictions and his personal lawyer/fixer’s convictions.

What’s more, as Barr conceded, the lack of an underlying crimes does not mean there can’t be obstruction. There can be other reasons you would obstruct an investigation, including that you are worried how the mere appearance of potential wrongdoing could hurt you politically — which Trump clearly had to be concerned about.

Another very important point. While Barr has emphasized that the White House cooperated extensively with the Mueller investigation, there were some areas in which the cooperation was less than complete. Trump didn’t submit to questioning, for instance, nor did his personal lawyers or Donald Trump Jr.

What’s more, when leaning on people to not testify truthfully (which Cohen has alluded to) or retaliating against people who run afoul of you (as Trump has done repeatedly), the point is to conceal potentially unhelpful evidence. The most successful obstruction means there will not be a provable underlying crime, because you were able to obscure it.

Barr has been careful to note that the lack of an underlying crime doesn’t mean there could be no obstruction, but his and others’ focus on this point has been curious, to say the least.

This, again, is very directly about Barr. He said this in his testimony last month: “But the point I was trying to make earlier is that in the situation of the president, who has constitutional authority to supervise proceedings, if in fact a proceeding was not well-founded, if it was a groundless proceeding, if it was based on false allegations, the president does not have to sit there, constitutionally, and allow it to run its course.”

As Amash correctly notes, Trump couldn’t possibly have known whether everyone being interviewed or investigated by Mueller had been involved in some crime. This investigation, after all, was not just about Trump; it was about Russian interference in the 2016 election, and it included the possibility that someone engaged in collusion or conspiracy with or without Trump’s knowledge. Mueller indicted dozens of Russians, and Trump associate Roger Stone is going to trial in connection with his outreach to WikiLeaks.

This is an undersold point in all of this.

And Amash lays waste to another argument against impeaching Trump. But unlike the others, this one actually isn’t so much about Barr. Instead, it’s about those who say Trump needs to be charged with a crime to be impeached. And it’s as much a rebuke to Trump’s defenders as some Democrats who have slow-walked the possibility of impeachment.

The first problem with this argument is that Mueller expressly didn’t rule out that Trump had committed a crime; instead he said it wasn’t his place to make that determination. And in fact, if you look closely at his report, there are five episodes that he seems to have found evidence to satisfy the three criteria for obstruction.

The second problem is that, as Amash notes, you don’t need an actual “crime” to impeach. Impeachment is an inherently political process that asks lawmakers to determine whether a president has violated a very undefined standard of misconduct in office. Bill Clinton was accused of several crimes by Kenneth Starr, and he was impeached but not convicted. Trump’s actions were problematic enough that Mueller determined he couldn’t clear him of obstruction, but even if none of that were criminal, it’s really up to Congress to decide.

Amash himself has now decided. And regardless of whether you think the case he makes is compelling, he brings up some valid points when it comes to the most frequently trafficked arguments against impeachment.