A federal judge on Monday ruled that President Donald Trump cannot block House Democrats' subpoena to obtain his financial records from accounting firm Mazars USA.U.S. District Judge Amit Mehta's ruling gives House Oversight Committee Chairman Elijah Cummings of Maryland an initial victory after Trump's attorneys sued last month to block his subpoena to obtain eight years of documents.The committee has said it wants the records to corroborate former Trump attorney Michael Cohen's testimony before Congress as well as to help investigate whether the president has any conflicts of interest with his businesses.Mehta heard arguments last week and decided not to rule from the bench but signaled that he'd make a quick ruling due to the gravity of the case. At the hearing, Mehta appeared skeptical of the Trump team's argument that Congress was overstepping its oversight authority and acting more like law enforcement than legislators."Applying those principles here compels the conclusion that President Trump cannot block the subpoena to Mazars," Mehta wrote in his opinion, noting that the committee wants the records to "assist in monitoring the President's compliance with the Foreign Emoluments Clauses" and "strengthening ethics and disclosure laws."These are facially valid legislative purposes, and it is not for the court to question whether the Committee's actions are truly motivated by political considerations. Accordingly, the court will enter judgment in favor of the Oversight Committee."The ruling on the Mazars subpoena was the first courtroom test for the White House as it refuses to comply with subpoenas. It could have future implications for the defiance of other subpoenas as Democrats likely head to court over obtaining Trump's tax returns.In a Monday evening statement, Cummings lauded the court’s decision, calling it “a resounding victory for the rule of law and our Constitutional system of checks and balances.”“The court recognized the basic, but crucial fact that Congress has authority to conduct investigations as part of our core function under the Constitution,” Cummings said.“Congress must have access to the information we need to do our job effectively and efficiently, and we urge the President to stop engaging in this unprecedented cover-up and start complying with the law.”But the district court is unlikely to have the final word, with Trump's team is expected to appeal Monday's ruling.