(Reuters) - President Donald Trump is flatly refusing to cooperate in numerous U.S. congressional probes of himself and his administration, taking a defiant stance that could trigger protracted court fights with House of Representatives Democrats.

U.S. President Donald Trump attends the 2019 White House Easter Egg Roll on the South Lawn of the White House in Washington, U.S., April 22, 2019. REUTERS/Shannon Stapleton

In an unprecedented step, the Trump administration has filed a lawsuit to try to block one congressional subpoena; some Trump advisers have been told to ignore other subpoenas; and a request for Trump’s tax returns has not been fulfilled.

In most instances, Trump risks trouble with Congress over subpoenas, “contempt of Congress” citations and civil enforcement actions in court.

Trump’s stonewalling has hardened since the release last week of a redacted report from Special Counsel Robert Mueller on the investigation of Russian interference in the 2016 U.S. presidential election.

Trump viewed the report as an exoneration because the special counsel did not charge him with conspiring with Russia or with obstruction of justice. However, the report detailed the Trump campaign’s welcoming of help from the Russians and his later efforts to thwart Mueller’s inquiry.

Like other senior Democrats who are treating the Mueller report as a road map for further investigations by Congress, House Oversight Committee Chairman Elijah Cummings accused the Trump administration on Wednesday of a “massive, unprecedented, and growing pattern of obstruction.”

The following are ways Trump has defied Congress in recent days:

MCGAHN

Don McGahn, former White House counsel, was a key witness in the Mueller probe and House Democrats want to hear from him. But the White House plans to assert executive privilege to prevent McGahn and other current and former administration officials from testifying to Congress, the Washington Post has reported.

UNREDACTED MUELLER REPORT

Parts of the Mueller report were redacted, leaving some questions unanswered. Democrats have issued a subpoena in an attempt to obtain the full report without redactions and evidence Mueller relied on. Attorney General William Barr must decide by May 1 whether to comply.

Barr has said he has a legal obligation to keep secret information obtained from grand jury proceedings, and that other redactions were necessary to protect U.S. intelligence sources and avoid harm to ongoing law enforcement matters.

TAX RETURNS

Unlike past presidents in recent decades, Trump has refused to make public his tax returns, raising questions about what is in them. Democrats are probing Trump’s past business dealings and possible conflicts of interest posed by his continued ownership of extensive business interests.

Treasury Secretary Steven Mnuchin failed to meet a congressional deadline on Tuesday for turning over Trump’s tax returns to the House tax committee, setting the stage for a possible court battle between Congress and the administration.

Mnuchin said he planned to make “a final decision” on whether to provide Trump’s tax records by May 6.

Legal experts said House Democrats could vote to hold Mnuchin or IRS Commissioner Charles Rettig in contempt of Congress if they ignore a subpoena, as a step toward suing in federal court to obtain the returns.

MAZARS

Trump on Monday filed a lawsuit attempting to keep U.S. lawmakers from obtaining his financial records. The unprecedented suit seeks to block a subpoena issued by Cummings, whose panel is looking into Trump’s financial record.

The subpoena sought eight years of documents from Mazars USA, an accounting firm long used by Trump to prepare financial statements. Cummings issued the subpoena after Michael Cohen, formerly Trump’s personal lawyer, testified to Congress in February that Trump had misrepresented his net worth.

SECURITY CLEARANCES

Cummings said on Tuesday that his panel will soon vote on whether to cite a former White House official with contempt for failing to appear for questioning on allegations that the Trump administration inappropriately granted security clearances to some of the president’s advisers.

The White House told the Oversight Committee that it had directed Carl Kline, who was White House personnel security chief for the first two years of Trump’s presidency, to ignore the committee’s subpoena to appear.

CENSUS AND CITIZENSHIP

On Wednesday, the Department of Justice (DOJ) rebuffed the Oversight Committee’s request for an interview with John Gore, an official who was involved in the administration’s decision to include a citizenship question in the 2020 census.

The Justice Department said Gore, a lawyer in its Civil Rights Division, would not participate in a deposition set for Thursday if he could not have a department lawyer at his side. The committee had offered to let a lawyer sit in a different room.

A DOJ official said the committee had provided “no legitimate or constitutional basis for excluding a DOJ lawyer from assisting at the deposition.”

IMPEACHMENT

Trump on Wednesday vowed to fight any effort by congressional Democrats to launch impeachment proceedings against him, promising to go to the Supreme Court, even though it plays no role in the constitutional impeachment process.

FBI ABOUT-FACE

Congressional Democrats said in March that a U.S. government agency was responding too slowly to their requests for documents about the Trump administration’s abandonment of a plan to move the FBI.

Before he became president in January 2017, Trump supported moving the Federal Bureau of Investigation headquarters to the suburbs of Washington, Democrats looking into the matter said.

They said that after Trump was elected and disqualified from bidding to acquire the site for commercial development, he switched his position. Democrats have subsequently raised questions about a possible Trump conflict of interest.

Trump’s about-face would “block potential competitors from developing the existing property on Pennsylvania Avenue across the street from the Trump Hotel,” the Democrats said.

IMMIGRATION AIDE

The White House refused a request for Trump’s top immigration aide Stephen Miller to testify to Congress in a letter on Wednesday to the House Oversight Committee.

Miller, a former Senate aide, has helped shape some of Trump’s most controversial immigration policies, from the first Muslim travel ban shortly after he took office in 2017 to the child separation policy for migrants who illegally crossed the U.S.- Mexico border, both of which were rejected by courts.