The GAO found that Obama broke the law at least 8 times.
And probably more than that. It's hilarious watching Democrats trip all over themselves to celebrate the recent, non-binding opinion of an outfit that, contrary to press spin, is far from "non-partisan". First, it's a creature of Congress. Second, it's largely staffed by leftists, like most of the civilian federal bureaucracy. Third, the current GAO director is an Obama appointee.
Plus on substance the GAO's claim is wrong to the point of being silly, and was strongly refuted by the OMB, which ruled temporarily withholding the aid was completely legal.
https://www.breitbart.com/politics/2019/12/13/omb-releases-memo-on-legal-reasons-to-withhold-ukraine-aid/
If someone tried to take the Trump administration to court on the GAO arguments they'd be laughed out of it.
The GAO found the Obama administration guilty of numerous crimes over the years, and the media barely mentioned it. Republicans complained but didn't push for impeachment. Democrats were hypocritically quiet.
One notable example was Obama's infamous swap of 5 Taliban Gitmo prisoners for traitor Bowe Bergdahl (whom the administration was at the time trying to hype up as a hero who had served with "distinction"), which blatantly broke the DoD Appropriations Act of 2014 and the Antideficiency Act in ignoring a requirement to notify Congress at least 30 days in advance of transferring Gitmo prisoners and in misappropriating funds.
https://www.breitbart.com/politics/2020/01/16/seven-times-the-gao-found-the-obama-administration-violated-federal-law/
https://www.gao.gov/assets/670/665390.pdf
Another was Obama's White House breaking laws explicitly forbidding certain science/space/military appropriations from being used in dealings with China, which the administration proceeded to use in dealings with China.
https://www.cnsnews.com/article/washington/terence-p-jeffrey/gao-obama-white-house-violated-law-engagements-china
https://cdn.cnsnews.com/attachment/GAO-OPINION-10-11-2011.pdf
Whereas the OMB disputed the recent anti-Trump GAO memo, the Obama White House didn't even dispute that it had violated the legal prohibition in the Chinese dealings. It instead just argued that the law, which had recently been passed by Congress and signed by Obama, was an unconstitutional infringement on executive power in "foreign affairs".
Apparently Democrats agreed. At the time. Guess it depends on who's president and which letter is by his name.