It was nearly three weeks ago when the House committee investigating the Jan. 6 attack made a bold and historically unusual move: The bipartisan panel subpoenaed five sitting Republican congressmen. The quintet, at least initially, said very little.

The members’ reticence led some to wonder whether the GOP lawmakers were open to the possibility of honoring the legal process. In fact, last week, 21 former House Republican lawmakers urged the subpoenaed members to cooperate with the investigation.

“We believe our country is at a pivotal moment. In the wake of the January 6th, 2021, attack on the U.S. Capitol, current Members bear a responsibility to do all they can to secure our institutions,” the former lawmakers wrote. “As part of that duty, we write to urge you to cooperate with the House Select Committee investigating the attack.”

The advice was not well received. The Washington Post reported:

House Minority Leader Kevin McCarthy (R-Calif.) issued a statement Friday indicating that he is unlikely to comply with a subpoena issued this month requesting that he testify before the House select committee investigating the Jan. 6, 2021, attack on the Capitol.

McCarthy’s lawyer, Elliot Berke, sent an 11-page response to the select committee late last week, questioning the panel’s authority and arguing that investigators are “not exercising a valid or lawful use of Congress’ subpoena power.” Just as notably, McCarthy’s counsel also asked the committee to turn over all kinds of information, including details on what investigators want to ask the GOP leader about.

This came on the heels of a related response from Ohio Rep. Jim Jordan, whose six-page letter last week said largely the same thing. He and McCarthy then wrote a joint op-ed for The Wall Street Journal, questioning the “legitimacy” of the Jan. 6 panel.

Any chance the other subpoenaed Republican members might be more open to compromise? Apparently not. Rep. Andy Biggs has also formally objected to the legal summons and released a copy of the letter his lawyers sent to the committee’s leadership. Among the arguments was the familiar claim that the panel is not constitutionally valid.

When NBC News caught up with the Arizonan over the holiday weekend, and asked about the subpoena, Biggs again said that he doesn’t perceive the bipartisan panel as “a legitimate committee.”

Rep. Scott Perry of Pennsylvania has also balked, while Rep. Mo Brooks announced over the holiday weekend that he would refuse to cooperate unless a series of demands are met.

“It’s got to be in public, it’s got to be congressman to congressman, it’s got to be limited to issues associated with Jan. 6, and it has to be after this Senate primary is over with,” the Alabama said.

Let’s take stock of a few things. Right off the bat, subpoenas are not casual suggestions or polite invitations, and those subpoenaed in federal investigations generally don’t respond by laying out a series of conditions they expect to be met before they consider whether to answers questions or not. A Washington Post report recently explained, “Subpoenas are legally binding requests to testify; violating them can carry a fine or jail time.”

Second, the questions about the legitimacy of the committee and its investigation have already been answered. As regular readers know, there is a process through which House members create select committees, and it involves the full chamber approving a resolution to create a panel and giving it the legal authority to issue subpoenas.

The House held such a vote last summer, approved the creation of the committee, and members from both parties were seated in accordance with the resolution.

In the months that followed, several federal judges — from district and circuit courts — have recognized the legitimacy of the investigatory committee and its work. In fact, earlier this year, when a federal judge had to consider the validity of the Jan. 6 panel, District Court Judge David Carter said in his ruling, “The public interest here is weighty and urgent…. Congress seeks to understand the causes of a grave attack on our nation’s democracy and a near-successful attempt to subvert the will of the voters.”

Earlier this month, Judge Tim Kelly, a Trump appointee, also used a ruling to endorse the validity of the panel and its subpoenas.

Republicans can keep throwing around the word “illegitimate,” but that doesn’t make it so.

And finally, the more these GOP members — each of whom are highly relevant witnesses — refuse to share what they know, the more it looks like they’re participating in a cover-up.