Democrats adored the Government Accountability Office press release reporting that Trump broke the law when he failed immediately to disburse the funds Congress had allocated to Ukraine.  It didn't matter that the GAO was in such a hurry to get the word out that it didn't have an opinion prepared.  What mattered was to smear Trump as quickly as possible.  Here, said Democrats in Congress and the media, was more proof that Trump must be impeached.

Fortunately, sensible conservatives have learned to wait before panicking.  Within hours, Joel Pollak was able to detail the seven times the GAO tagged President Obama for breaking federal laws without any repercussions:

Nevertheless, if a mere GAO finding is sufficient to justify impeachment, then President Barack Obama ought to have been impeached at least seven times over for each of the following cases in which the GAO found that the Obama administration had violated federal law.

• The Department of Homeland Security (DHS) and United States Secret Service (USSS) were found to have violated section 503 of the Consolidated Security, Disaster Assistance, and Continuing Appropriations Act, and the Antideficiency Act, in 2009 after the Secret Service reported that it had overspent on candidate protection in 2008 by $5,100,000, and used money from another program to cover the shortfall. DHS failed to notify Congress 15 days in advance of the "reprogramming."
• The Department of the Treasury was found to have violated the Antideficiency Act in 2014 when it used the voluntary services of four individuals. "Treasury did not appoint any of the individuals to federal employment, nor did any individual qualify as a student who may, under certain circumstances, perform voluntary service," the GAO found, adding that there was no emergency that might have justified using the individuals to perform several months of work without receiving pay.
• The Department of Defense was found to have violated the Department of Defense Appropriations Act of 2014 and the Antideficiency Act in the infamous Bowe Bergdahl swap, when President Barack Obama traded five high-level Taliban detainees for a U.S. Army deserter. The administration transferred the five Taliban from Guantanamo Bay without notifying relevant congressional committees 30 days in advance, as required by law. Republicans complained; Democrats were silent.

(You can see the other four violations here.)

It's also entirely possible that the GAO's anti-Trump animus led it into making a legal error.

The money for Ukraine was part of Public Law 116-6, which Trump signed in February 2019.  The law does not state deadlines for releasing some or all of the funds.  It says only that the funds must be disbursed before the end of the fiscal year.  Trump released them in September 2019, long before the fiscal year ended.

The Impoundment Control Act of 1974 ("ICA"), which the GAO cites to support its eventual decision, states a procedure if the President will hold onto the funds after the fiscal year ends.  However, the ICA's language does not require the president to release the funds at a specific point before the fiscal year ends.  Nor is there any language stating that the president must notify Congress if he merely considers taking advantage of the procedure to delay disbursing funds until after the fiscal year ends.

The GAO also errs when it claims that the ICA does not allow temporary holds on funds during the fiscal year for "policy reasons."  That's not in the ICA, and 2 USC §683 states the opposite (emphasis added):

Whenever the President determines that all or part of any budget authority will not be required to carry out the full objectives or scope of programs for which it is provided or that such budget authority should be rescinded for fiscal policy or other reasons.

In other words, it appears that the GAO cherry-picked legislative history to add restrictions that are not in the statute's plain text, which is a no-no in statutory interpretation.  Moreover, David Rivkin points out that presidents have often used foreign policy decisions (which are part of their constitutional purview) to determine how to disburse foreign aid:

Thomas Jefferson impounded funds appropriated for gunboat purchases, Dwight Eisenhower impounded funds for antiballistic-missile production, John F. Kennedy impounded money for the B-70 bomber, and Richard Nixon impounded billions for highways and urban programs. Congress attempted to curtail this power with the Impoundment Control Act of 1974, but it authorizes the president to defer spending until the expiration of the fiscal year or until budgetary authority lapses, neither of which had occurred in the Ukraine case.

The GAO is apparently so busy policing Donald Trump that it failed to police itself.

UPDATE: Alan Dershowitz agrees that the GAO is wrong. He focuses solely on the constitutional, rather than the statutory, reasons: 

U.S. Government Accountability Office (GAO) has gotten the constitutional law exactly backwards. It said that the "faithful execution of the law" — the Impoundment Control Act—"does not permit the president to substitute his own policy priorities for those congress has enacted into law ." Yes, it does — when it comes to foreign policy. The Constitution allocates to the president sole authority over foreign policy (short of declaring war or signing a treaty). It does not permit Congress to substitute its foreign policy preferences for those of the president.

To the extent that the statute at issue constrains the power of the president to conduct foreign policy, it is unconstitutional.