Washington (CNN) Since House Democrats announced a formal impeachment inquiry into President Donald Trump last month, Congressional Republicans have attempted to push back on everything from the basis for the inquiry to the process itself. A handful of Republicans have been increasingly vocal about what they say has been an unfair, secretive process. This week, those GOP grumblings turned into action.

On Wednesday, approximately two dozen House Republicans, led by Florida Rep. Matt Gaetz, crashed a secure room in Congress where a closed hearing was underway as part of the House's impeachment inquiry into the President. According to CNN's Manu Raju , some of the conservatives entered the room yelling and calling the process a sham.

A committee official told CNN that the House Republicans violated House deposition rules by entering the secure room, known as the Sensitive Compartmented Information Facility, or SCIF . They also criticized the Republican members for bringing in their phones and other electronics, which goes against the rules of a SCIF and opens up the classified topics discussed wherein to tap-able recording devices.

Adding to the chorus of complaints, South Carolina Rep. Sen. Lindsey Graham on Thursday called the impeachment proceedings in the House "unfair and dangerous."

Crashing hearings is not unprecedented. In fact, Gaetz himself has been refused entry to impeachment hearings before, since he is not a member of any of the committees conducting the inquiry. But this latest attempt violated procedural rules and caused a major security breach to protest a difference in opinion over the proper process for impeachment.

However, formal impeachment proceedings are rare, so the process is based predominantly on precedent, rather than steadfast rules. According to the Congressional Research Service , "Should a simple majority of the House approve articles of impeachment specifying the grounds upon which the impeachment is based, the matter is then presented to the Senate, to which the Constitution provides the sole power to try an impeachment."

Contrary to the complaints, the impeachment proceedings have not been entirely irregular. Here are some facts and context behind the Republicans' complaints.

Formal vote

One aspect of the House's current proceedings that Republican leaders have criticized is the lack of a full House vote to authorize the impeachment inquiry. In a letter , House Minority Leader Kevin McCarthy said continuing the inquiry without a vote would render the process "devoid of any merit or legitimacy."

While the House voted to launch a formal impeachment inquiry in the case of both Presidents Richard Nixon and Bill Clinton , Democrats say the Constitution does not require any such vote to conduct an inquiry. Furthermore, recent changes to subpoena powers mean the Democratic-majority House committees leading the inquiry already have that tool at their disposal.

Location of the hearings

Rep. Jim Jordan criticized the secretive nature of the hearings, telling Fox News 's Bill Hemmer and Sandra Smith that "it's all being done in the basement of the Capitol where no one in the country can see."

The hearings are taking place in the SCIF, a secure space on Capitol Hill often used for classified briefings, which is located in the basement of the Congressional Visitor's Center. The SCIF is where the House Intelligence Committee — which is leading the impeachment investigation — conducts its work. It's the same space where the Republican-led Intelligence Committee conducted interviews for the Russia investigation in the last Congress.

Although normally committee hearings must be open, members can vote to close the hearing under specific circumstances. According to House rules , a hearing should be closed if the "disclosure" of the witnesses would defame or incriminate someone, endanger national security, compromise sensitive law enforcement info, or violate a House rule.

Investigations into Nixon and Clinton also both featured closed door depositions before public hearings. Democratic Rep. Adam Schiff, Chairman of the House Intelligence Committee, has said the committees will hold public hearings after the initial round of closed-door interviews.

Schiff told reporters it was important the hearings were closed so as to prevent witnesses from overhearing and influencing each others' testimony, similar to the rationale used in criminal investigations.

Selective leaks

President Trump has also criticized the Democrats' impeachment hearings for "selective leaks," writing on Twitter that they were "allowing no transparency."

It's not true that there has been "no transparency." The names of scheduled and subpoenaed witnesses are public. Additionally, the opening statements of several witnesses have been made available after their testimony.

Schiff has said he plans to release transcripts but has not specified when.

However, it is true that some information has been leaked, but both Republicans and Democrats have a long history of leaking information when convenient, as well as ridiculing leakers when the info is inconvenient. And some of the leaks, such as opening statements, have come from the witnesses themselves, including one that was issued as a press release.

Barring lawyers

On Fox, Jordan claimed , "In the interviews, no White House lawyers can be there, no agency lawyers can be there."

It's true that White House lawyers are not participating, but barring them is not surprising nor unusual for hearings of this nature.

To justify his decision, Schiff has said he is conducting these preliminary hearings like grand jury testimony. And Republicans will have their chance to allow White House lawyers to participate should the impeachment inquiry go to trial in the Senate.

However, to Jordan's point, for the closed-door sessions during the Nixon impeachment investigation, the President's lawyer was allowed to participate and cross-examine witnesses.

Hearing procedure

On October 16, McCarthy accused the Democrats of preventing Republicans from cross-examining witnesses during these hearings.

Schiff said this is inaccurate, and that he has been conscientious about "giving the GOP members every opportunity to ask questions."

McCarthy's fellow Republican Rep. Mark Meadows told The Washington Post that each side alternates asking questions in set time blocks and that there has been no limit provided for the number of questions each side can ask the witnesses.

Normal procedure dictates that the chair of the committee gets the first statement, then the ranking member or another member of the minority, followed by the witnesses opening statement.

Thus far, staff attorneys for both parties have led the majority of the questioning, with members adding in their own questions, too. Lawmakers and aides have told CNN the Democrats and Republicans have traded off hourlong and 45-minute rounds until all of their questions have been exhausted, meaning both sides have equal time.

Republicans calling witnesses

Jordan told Fox News the Republicans "can't get the witnesses we want to call."

This is because the House Republicans are in the minority and as such, they do not have subpoena power.

In both the Nixon and Clinton impeachment inquiries, language in the resolution granted the minority party this power, but with a caveat: subpoenas were voted upon by the committee, which meant the majority, in theory, had the power to block subpoenas proposed by the minority.