Yascha Mounk, who studies populism and democracy and teaches at Johns Hopkins University, called the vote “yet another example of European institutions — lacking not only the courage of their convictions, but any kind of conviction — caving to authoritarian powers.”

Alina Polyakova, a scholar at the Brookings Institution, said: “Since 2014, Russia has only stepped up its repressive behavior at home and aggressive actions abroad. The decision to allow Russia back into the Council sends the message that this behavior is acceptable. It’s a dangerous precedent for others.”

Before the vote, Dr. Polyakova noted: “Since the invasion of Crimea in 2014, Russia has: invaded the Donbas, supported Assad in Syria, interfered in the US and Europe’s election, attempted to murder the Skripals, and more. How does this behavior justify membership in the Council of Europe?”

Created in 1949 and based in Strasbourg, France, the Council of Europe is dedicated to upholding democracy, human rights and the rule of law in its 47 member states, which include all 28 members of the European Union, and encompass a population of more than 800 million. The European Court of Human Rights, part of the council, is charged with enforcing the 1953 European Convention on Human Rights, which all members are pledged to uphold.

The organization is made up of the foreign ministers of all member states and a parliamentary assembly of member legislators. They voted to lift Russia’s suspension after the foreign ministers agreed to do so in May, in a deal worked out by Germany and France.

Heiko Maas, the German foreign minister, said that the compromise would ensure “millions of Russians the protection of the European Court of Human Rights.” France and Germany had argued that it was better to promote dialogue, especially in the face of fundamental disagreements.