Trump's peace talks with Putin: "Ger­many must not recog­nize a dic­tated peace in Ukraine"

Hier geht es zur deutschen Version des Interviews.

LTO: Professor Aust, three years ago Russia started its invasion of Ukraine. Donald Trump promised to end the war but so far, his peace talks only included Vladimir Putin. What can he achieve without Ukraine present in these negotiations?

Prof. Dr. Helmut Philipp Aust: I wonder the same. One basic requirement for any peace treaty is the participation of both parties to the armed conflict, so there cannot be peace without participation of Ukraine. The US president and the Russian president can talk about some basic conditions in preparation for negotiations between Russia and Ukraine. However, this does not seem to be the motivation of Donald Trump.

“The US and Russia cannot decide that Ukraine loses parts of its territory”

Which binding agreements can be made without including Ukraine? Can two states conclude an agreement that binds a third party?

The Vienna Convention on the Law of Treaties clearly says that any contract may not be concluded at the expense of third parties. This means that Russia and the US cannot decide on the cession of parts of the Ukrainian territory, as should be obvious to everyone.

What can Russia and the US decide together? 

Russia and the US can conclude binding agreements on issues that concern only them, for example ending US sanctions on Russia. The sanctions are part of economic relations the US has with Russia and they can decide for themselves what kind of relations they want to have. Lifting sanctions, however, would be unfortunate, after all these sanctions are supposed to force Russia to respect the prohibition of the use of force. 

Europe is "not willing to compensate for loss of US support"

Contrary to what Donald Trump said, Ukraine did not start the war. Russia attacked and continues to attack Ukraine and therefore bears the responsibility for the ongoing war. How can Ukraine still be brought to the negotiating table?

Ukraine is in a difficult position. It cannot count on continued US support, Donald Trump made that clear through his distorted claims about the conflict and his overall erratic behavior. At the same time, Ukraine's war effort still depends on US military aid as European countries don't seem to be willing or able to effectively compensate for a possible loss of US support.

It is therefore possible that Ukraine will sooner or later have to bite the bullet and engage in peace talks organized by Russia and the US. But even that is difficult to predict right now, because the behavior of the US administration has become so erratic that anything seems possible.

What do you think should be the next step in these peace negotiations?

Right now, there are no real peace negotiations. First of all, they don't involve Ukraine. Second, I don't think the talks between Trump and Putin can even be described as negotiations. Negotiation means discussing and finding a compromise, and in that process all parties make concessions. Trump, however, just seems to be offering Putin what he has been demanding since the beginning of the conflict. 

Is there a way to end this show and create a real negotiations table where Ukraine can take part and make its own demands?

The most promising way would be for Ukraine and its European allies to agree on a position, that can be the groundwork for negotiations with Russia and the US. I think, European countries have to take a stand here, especially with regard to how strong their commitment to supporting Ukraine really is. Under the Trump administration they no longer can rely on the US. This was made clear once again by the Vice President's speech at the Munich Security Conference. 

"Peace is usually negotiated during an ongoing war" 

To take a broader perspective, how can you negotiate a treaty that creates peace in the long term? What are the basic conditions?

There is no one-fits-all solution to this issue. The international community has had little experience with peace agreements in international armed conflicts in recent years.

As a starting point: Political science suggests that peace is usually negotiated during an ongoing war. The idea that the parties will lay down their weapons before sitting down to negotiate is unrealistic, as my colleague Cindy Wittke has shown in her book "Law in the Twilight".

For Ukraine to achieve a just and sustainable peace, it must come to the negotiating table in the strongest possible position.

By "strong position" do you mean their military position? Do they have to continue fighting before negotiating?

That is, of course, ultimately up for Ukraine to decide. Just as Ukraine should not be pressured from outside to accept an unfavorable position for a peace agreement, it should not be expected to continue fighting. Third parties should not intervene in either way.

"Begin with 'islands of agreement'"

Let's look at the content of a possible peace treaty: The parties probably won't agree on every question.

No. But it can help to create so called "islands of agreement", i.e. agreements on individual issues that are most important to the parties.

The term was established by Gabriella Blum who is a professor for international law at Harvard Law School. The approach has already worked for the war in Ukraine, for example with prisoner exchanges or the now expired "grain agreements".

What else must be taken into consideration? 

One key question is how to satisfy the understandable wish for peace while keeping up basic norms of international law. 

"Treaties reached by force are void"

What does that mean exactly?

Since at least 1945, international law prohibits territorial changes through the use of force. Accordingly, treaties between states are void when they were reached by force.

Russia first annexed Crimea in 2014, and later the regions Luhansk, Donetsk, Zaporizhzhia and Kherson. Russia wants to keep those territories, and Donald Trump has already suggested that Ukraine may have to cede territory to reach an agreement. There is room to disagree on the details but overall, a binding peace agreement that includes territorial concessions would go against fundamental principles of the international legal order. Third countries like Germany must not recognize territorial changes that were reached by force in violation of international law.

But it is hard to imagine that Russia will give up the annexed territories.

Yes. That is why even in the case of a war of aggression you have to make compromises trying to end the war. Further negotiations will show how those compromises will look.

What is important in the end, is that it is Ukraine's decision. Ukraine has a president who was elected in democratic elections – contrary to what Donald Trump has suggested recently – and he has the power to decide this, together with the other Ukrainian institutions. It sounds like a phrase, but it is true from the standpoint of international law: Only Ukraine can decide over its fate. Every country has a right to defend its territorial integrity and sovereignty.

The interview was carried out in writing. This text is a translated and slightly revised version of the interview published in German on February 24, 2025.

Professor Dr. Helmut Philipp Aust is a professor of public and international law at Freie Universität Berlin.