“Military action against Ukraine by forces of the Russian Federation is a breach of international law.”
Nato secretary general Anders Fogh Rasmussen

There appears to be broad agreement in the west that Russia is breaking international law by occupying the Crimea peninsula, although Vladimir Putin insists otherwise.

Sending troops into Ukrainian territory would appear to be a breach of a number of international legal instruments including the 1991 Minsk Agreement (which formally dissolved the Soviet Union) and the 1994 Budapest Memorandum on Security Assurances.

The Budapest Memo saw Russia, the US and the UK promise to respect Ukrainian sovereignty and refrain from using or threatening force against the country, in exchange for Ukraine giving up what was at the time the world’s third largest stockpile of nuclear weapons.

Despite fears that the document could drag Britain and America into the conflict, there is nothing in the wording of the Budapest agreement that commits the parties to defending Ukrainian sovereignty.

Mr Putin says Russia’s actions are legal and his argument appears to depend on three things. First, he says the armed men who have surrounded Ukrainian forces on the Crimean peninsula are not Russian soldiers but “local self-defence forces”.

This has been met with widespread incredulity, and if Russia has in fact sent in troops without identifying themselves properly, this could be a further breach of international law, according to Dr Jonathan Eyal of the Royal United Services Institute.

Second, Mr Putin says the new government of Ukraine is illegitimate. He says the ousted Viktor Yanukovych is still the legitimate leader of Ukraine, and he has formally asked Russia for military assistance.

The Russian president says regime change in Ukraine means Russia cannot be breaking the Budapest Memorandum, saying: “We didn’t sign any documents with this government.”

International law expert Professor Marc Weller from Cambridge University said Yanukovych had “lost effective authority and could no longer claim to be the president” when he asked Russia to intervene.

It’s true that Ukraine’s parliament did not follow the correct impeachment procedures against Mr Yanukovych but it can nevertheless reasonably claim to represent the will of the majority of Ukrainians, he said.

He also poured cold water on Mr Putin’s third point: that Moscow has a legal right to intervene to protect ethnic Russians from attacks by Ukrainian nationalists. Prof Weller says we are not talking about Russian citizens, there is no evidence of extremist attacks and even if there were, “the remedy would hardly be an armed intervention on foreign territory”.

But Prof Weller also said the fact that Russian forces have so far not resorted to violence (apart from warning shots) could be important in terms of international law.

Under Article 51 of the UN Charter Ukraine has the right to defend itself if subject to “an armed attack”. But if force is not used, it could be argued that the Russian mobilisation does not constitute an “attack”.

Mr Putin said today that the open use of force would still be “fully legitimate and be in line with international law”, but it is difficult to see what the legal justification would be.

“There has been a lot of speculation regarding movements of troops of the Russian Black Sea fleet, taken as a precautionary measure in full compliance with the relevant bilateral agreements with Ukraine.”
Russian embassy statement

This is a reference to the 1997 deal where Russia agreed to lease naval facilities on the Crimean peninsula. Russia has said it is within its rights to deploy troops in the region.

The full text of the agreement is here.

While it is true that up to 25,000 Russian navy personnel are allowed in Crimea under the deal, the agreement states clearly that they can only be deployed on Russian bases and must act in a manner “respecting the sovereignty of Ukraine, observing its laws and permitting no interference in the internal affairs of Ukraine”.

The agreement also states that troops crossing the border have to identify themselves by showing military ID.

Clearly the actions of Russian troops – if that is who they are – in recent days is in breach of these clauses.

It also violates a broader agreement on friendship signed in 1997, which states that Russia and Ukraine should “build their relations on the basis of principles of mutual respect of sovereign equality, territorial integrity, inviolability of borders, peaceful settlement of disputes, non-use of force or threat of force…”.

“Political power in Kiev has been concentrated in the hands of far-right extremist elements that do not hide their xenophobic, anti-Semitic, neofascist credentials.”
Russian embassy statement

There are undoubtedly far-right politicians in the Ukrainian interim government formed after Yanukovych fled the country, although it may be an exaggeration to say that power is “concentrated in their hands”.

The moderate Fatherland Party leader Arseniy Yatsenyuk will lead the cabinet until presidential elections on 25 May. His deputy prime minister is Oleksandr Sych of Svoboda, an ultranationalist party with links to the British National Party and the Hungary’s Jobbik.

Party leader Oleh Tyahnybok has a history of making anti-Semitic comments and has said that Ukraine is controlled by a “Muscovite-Jewish mafia”. Svoboda members have also taken the posts of ecology minister, agriculture minister and prosecutor general.

Overseeing Ukraine’s armed forces is the new secretary of Ukraine’s National Security and Defense Council Andriy Parubiy, who helped found the Social-National Party of Ukraine, the openly neo-fascist precursor to Svoboda.

His deputy is Dmytro Yarosh, another Euromaidan organiser who leads the far-right paramilitary group Right Sector.

“We are strong enough to defend ourselves.”
Ukrainian ambassador to the UN, Yuriy Sergeyev

Various assessments of the respective military strength of Ukraine and Russia have emerged in recent days, most based on figures from the International Institute for Strategic Studies.

Russia has an estimated 845,000 soldiers ready to deploy, compared to 129,000 in Ukraine. Russia is also thought to have twice as many tanks in the field – about 2,500 compared to 1,100.

And Russia boosts huge air superiority, with nearly 1,400 fighter jets compared to about 220 for Ukraine.

Experts have cast doubt on the battle-readiness of Ukrainian forces and raised fears that some pro-Russian units might defect if fighting broke out.

On paper, Ukraine has four times as many soldiers and five times as many tanks as Georgia, whose military was quickly overwhelmed by Russia in the 2008 South Ossetia war, and Ukraine’s size would make a full-scale invasion a massive strategic challenge even for Russia’s formidable armed forces.