Who on the Ukrainian side can sign a memorandum with Russia?
The Russian Foreign Ministry's Legal Director said that the new leadership to sign the memorandum must be chosen by the Ukrainian people and Mr. Volodymyr Zelensky is not suitable for this role.

According to TASS on May 22, Director of the Russian Foreign Ministry's legal department Maxim Musikhin said that the Ukrainian people must elect a new leadership to sign the memorandum with the Russian Federation; the head of parliament may not be legally qualified to take on the role of signatory.
“It is important whose signature is on the documents, because now their “leadership” has long lost its internal legitimacy, not to mention external legitimacy. Accordingly, there may be questions about the validity of any agreement signed by such a person,” said Maxim Musikhin, director of the Russian Foreign Ministry’s legal department.
According to the diplomat, one must be absolutely sure that the settlement agreement is signed on the Ukrainian side by "a person with the people's authority to do so, otherwise there will be problems."
Mr Musikhin stressed that leader Vladimir Zelensky was not suitable to be a signatory. "The Ukrainian people must freely choose their new leader," he continued. "Then there will be a legitimate signatory. And now we are talking about some internal requirements of the Ukrainian constitution. Theoretically, if we consider it formally, the head of parliament has some authority to sign. Whether he is allowed to do this in his own country is a big question."
According to the Russian diplomat, the memorandum discussed during the conversation between Russian President Vladimir Putin and US President Donald Trump "will need the appropriate signatory", but "this is currently the problem". Mr. Musikhin also pointed out that it is necessary to consider all signatories of the settlement documents.