In response, Hungary's government said the EU Commission was motivated by Hungary's anti-migrant positions, including its court challenge to an EU plan to resettle asylum-seekers among the 28 members of the bloc.
They threw paper planes - alluding to allegations in Orban-friendly media that Soros had flown in foreign protesters.
Brussels said Austria had made a decision to join the relocation programme after being previously exempted as it had taken in 90,000 asylum seekers in 2015 thanks to its position on one of the key migratory routes into Europe.
Wednesday's protests were the fourth major demonstration in the past two weeks as the government faces growing resistance a year before elections are due.
Soros' vision of an open society contrasts strongly with Orban's conservative, anti-immigrant views, and Orban sees these groups as working against Hungarian interests.
Frans Timmermans, the first vice president of the European Commission, said Tuesday that Hungary must follow the values set out in Article 2 of the Treaty on European Union of "human rights including human dignity, freedom and equality, and societies which are defined by pluralism, non-discrimination, tolerance, justice and solidarity".
CEU itself was taken by surprise at Palkovics' comments, according to an emailed statement.
"The situation for asylum-seekers in Hungary, which was already of deep concern to UNHCR, has only gotten worse since the new law introducing mandatory detention for asylum-seekers came into effect", Grandi said.More news: Lowry bounces back, Raptors edge Bucks to even series at 1-1
"CEU has not been approached directly by secretary Palkovics with this information".
The new rules would require, among other things, the CEU to open a campus in the state of NY as well as reach an inter-governmental agreement with the U.S. Federal government, even though higher education is a state subject in the U.S., Ms. Innes said. Hungarian government spokesman Zoltan Kovacs said the law could not be suspended but that the government is open to holding talks on the issue.
"Exchanges in the press are no substitute for sustained direct contact on a confidential basis", the university said.
Both of those conditions would have been prohibitive by a deadline of January 2018, and CEU rejected them from the start.
Domestic opponents of the new law, which on Sunday triggered some of the largest demonstrations against Orban's seven-year rule, consider it part of a wider crackdown on dissent and a political drift towards Russian Federation.
The EU executive has "resolved to use all the instruments at our disposal under the Treaties to uphold the values on which our Union is grounded", Timmermans told reporters.
"The legislation, we believe, can also similarly threaten the operations of other American universities with degree programs in Hungary, so it goes beyond just Central European University", Toner said in a news conference.