President Donald Trump is arguing that the Manhattan district attorney's criminal investigation into his financial matters is unconstitutional, according to a complaint filed in the Southern District of New York on Thursday.

In the complaint, which was unsealed Friday, Trump's lawyers quoted a 1997 article by Jay Bybee, who is now a judge on the U.S. Court of Appeals for the Ninth Circuit, saying that the president "is the only person who is also a branch of government."

Trump lawyers argued that the writers of the U.S. Constitution did not intend for the president to be subject to criminal prosecution, because it could interfere with the functioning of the executive branch.

Quoting Article I, Section 3 of the Constitution, they argued that a president cannot be "liable and subject to indictment, trial, judgment and punishment" until he has already been convicted by the Senate through impeachment.

Allowing Vance to move forward would let him circumvent the Constitution's rules regarding impeachment, they wrote.

The complaint also describes attempts to reveal Trump's financial information as politically motivated attacks, in which New York government officials have played a "willing and eager" role.

"Throughout President Trump's time in office, government institutions, both federal and state, controlled by or aligned with the Democratic Party have attempted to use their power to obtain and expose his confidential financial information in order to harass him, intimidate him and prevent his reelection," Trump's legal team wrote.

In the complaint, Trump's lawyers describe the details of two grand jury subpoenas issued by Vance's office in August.

The first one requested information about alleged payments and communications between a list of people in Trump's orbit and two women who say they had sexual relationships with the president in the 2000s, which Trump denies.

Trump's legal team produced some documents in response, according to the complaint. But Vance's office said it believed the subpoena covered the Trump Organization's tax returns, and that impasse derailed the production of documents.

A second subpoena filed at the end of August was aimed at Trump's accounting firm Mazars USA, and it requested tax returns and other financial records for Trump, his companies and his foundation from Jan. 1, 2011, to the present, according to the complaint.

That subpoena is unconstitutional, Trump's lawyers argued in their complaint, calling on the federal court to block it.

The case has been assigned to U.S. District Senior Judge Victor Marrero.

Harry Sandick, a white-collar defense lawyer at Patterson Belknap Webb & Tyler, said he was surprised Trump's lawyers didn't go into more detail about why they're pursuing the case in the Southern District of New York, when the subpoena was filed in state court.

He said he expects Vance to address that in his office's response, which is due at the close of business Monday.

Trump's legal team is expected to respond Tuesday, and a hearing is set for 9:30 a.m. Wednesday. Vance has agreed to stay enforcement of the Mazars subpoena until 1 p.m. Wednesday, according to court documents.

Sandick said there's a big difference between indicting a sitting president and serving a grand jury subpoena, which may or may not ever lead to criminal charges.

Media reports indicate that Vance is investigating at least two angles related to Trump and the Trump Organization: whether business reports were illegally falsified, and the alleged payment of hush money to an adult film actress who said she had an affair with Trump in 2006. Trump has denied the accusation of an affair.

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