The GAO says Chad Wolf and Ken Cuccinelli are in their positions illegally

This should provide some explosives.

The Vacancies Reform Act permits certain individuals to serve as acting officials in vacant presidentially appointed, Senate confirmed positions (PAS) for limited periods of time. 5 U.S.C. §§ 3345, 3346. The Vacancies Reform Act is generally the exclusive means for filling a vacancy in a PAS position unless another statute provides an exception.2 Pursuant to the Vacancies Reform Act, the first assistant to a PAS position automatically becomes the acting official in case of a vacancy unless the President designates another individual who meets the Vacancies Reform Act’s eligibility requirements.

[...]

Upon Secretary Kirstjen Nielsen’s resignation on April 10, 2019, the official who assumed the title of Acting Secretary [Kevin McAleenan] had not been designated in the order of succession to serve upon the Secretary’s resignation.

[...]

Mr. McAleenan did not have the authority to amend the Secretary’s existing designation.

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Because the incorrect official assumed the title of Acting Secretary at that time, subsequent amendments to the order of succession made by that official were invalid and officials who assumed their positions under such amendments [...] were named by reference to an invalid order of succession.

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[U]pon the resignation of Secretary Kirstjen Nielsen, the express terms of the then existing designation required the Director of the Cybersecurity and Infrastructure Security Agency (CISA) to assume that title instead of the Commissioner of Customs and Border Protection (CBP), Kevin McAleenan. As such, the subsequent appointments of Under Secretary for Strategy, Policy, and Plans, Chad Wolf and Principal Deputy Director of U.S. Citizenship and Immigration Services (USCIS) Ken Cuccinelli were also improper because they relied on an amended designation made by Mr. McAleenan.

[...]

We have not reviewed the legality of other actions taken by these officials; we are referring the matter to the Inspector General of DHS for review.

  Government Accountability Office

Let the fireworks begin.

Circumventing the Senate now

The point is to usurp all the power of Congress.  Loyalty only goes one way with Trump, and he intends for everyone to understand that.

The White House has found a way to bypass a federal statute that dictates who can fill secretary positions, potentially allowing President Trump to choose whomever he wants to lead the Department of Homeland Security, according to an administration official.

[...]

After Kevin K. McAleenan, the acting secretary who had a tumultuous relationship with the White House, announced this month that he would resign, it was widely believed in the administration that Mr. Trump would tap someone who would not question his more extreme policies.

[...]

But officials leading agencies in homeland security who echo Mr. Trump’s fiery language on immigration were initially deemed ineligible under the federal Vacancies Act. The law states that acting officials who take over cabinet-level positions must be next in the line of succession, have the approval of the Senate or have served 90 days under the previous secretary.

The White House, however, is exploring a loophole in the law, according to an administration official. Under this route, the White House would tap someone to be the assistant secretary of the Countering Weapons of Mass Destruction Office, which is vacant, and then elevate that person to be the acting secretary of homeland security.

[...]

This year the Trump administration has purged, installed and transferred leaders in the department, sowing chaos among its ranks and creating a legal maze on personnel matters. The latest dubious workaround would mean that Mr. Trump has found a way to use the many holes in the department to fill a void.

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Mark Morgan and Kenneth T. Cuccinelli II, who both joined the department in recent months in an acting capacity, were thought to be out of the running for the job after the Justice Department’s Office of Legal Counsel advised that their appointment would violate the Vacancies Act. Neither Mr. Morgan, the acting commissioner of Customs and Border Protection, nor Mr. Cuccinelli, the acting director of the agency overseeing legal immigration, was confirmed by the Senate or served for at least 90 days under the last Senate-confirmed homeland security secretary, Kirstjen Nielsen.

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Mr. Cuccinelli has a tumultuous relationship with Senator Mitch McConnell of Kentucky, the majority leader. [...] Mr. Cuccinelli endorsed an effort by hard-line conservatives to force Mr. McConnell to step down and backed Mr. McConnell’s primary challenger in 2014.

  NYT

They were doing this back in 2017.

...but hey, do what you want...you will anyway.

UPDATE:

Cuccinelli once headed the Senate Conservatives Fund, an organization critical of the establishment GOP that ran primary campaigns against incumbents. That past has not been forgotten: Senate Majority Leader Mitch McConnell (R-Ky.) said earlier this year that he has a "lack of enthusiasm" for Cuccinelli and warned in April about nominating Cuccinelli to the permanent position.

McConnell stood by those remarks in a brief interview on Wednesday: “I don’t think I have anything to add to what I said about that earlier."

[...]

“The White House would be well advised to consult with the Senate and senators before they take any decisive action that might be embarrassing to Mr. Cuccinelli or to the White House itself,” said Sen. John Cornyn (R-Texas), who called the attempt to fill the top role at the department without Senate confirmations a “concern.”

[...]

Cuccinelli, acting head of the relatively obscure U.S. Citizenship and Immigration Services, is one of the president’s top lieutenants because of his aggressive immigration agenda. But he is loathed by McConnell and other Republicans to the point that he probably could not be confirmed for a permanent job.

  Politico

We don't need no steenkeen confirmation

The Trump administration is pushing the limits of an obscure federal law that restricts nominees from serving in federal positions before they’re approved by the Senate.

A POLITICO review has identified four officials at three different agencies [Environmental Protection Agency, the State Department and the White House Office of Management and Budget] doing substantially similar work to the position for which they have been nominated – despite not yet getting a green-light from the Senate.

[...]

A White House official said the administration is following federal guidelines that let it name nominees to separate "advisory or consultative" roles as they await confirmation for a position. The administration is "confident that all of the president's acting designations were made in accordance with the Vacancies Reform Act," the official said.

[...]

Passed by Congress in 1998, the Vacancies Act was written in response to an effort by then-President Bill Clinton to install an official at the Justice Department in an acting capacity even after he was rejected by the Senate.

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Asked for comment, EPA spokeswoman Liz Bowman said, “This is not unique to our administration, but something that is a common practice.”

  Politico

So who cares if it's illegal?

...but hey, do what you want...you will anyway.