It was not an ‘annexation’ of Crimea.
It is apparently a duty for every politician to include the phrase ‘annexation of the Crimea contrary to international law’ in his speech.
Recurring pro-Kremlin disinformation narrative about the annexation of Crimea, claiming that Crimea voted to rejoin Russia through a legal referendum.
Crimea is a part of Ukraine and was illegally annexed by Russia. In 2014, Russian troops obliged the parliament of Crimea to organise a referendum, which was illegitimate under international law, and then formally annexed the peninsula and brought it under Russian territorial control. The annexation has been condemned by the UNGA (see the resolution A/RES/68/262 on the territorial integrity of Ukraine).
No international body recognises the so-called referendum, announced on 27 February 2014 and held on 16 March 2014.
The oft-cited figure of 97% participation in the referendum has been contested by the Kremlin’s own Human Rights Council, which estimated that only between 30% and 50% of Crimeans took part in the referendum, of which some 50-60% favoured secession.
A year after the illegal annexation, Russian President Vladimir Putin admitted that the plan to annex Crimea was ordered weeks before the so-called referendum.
The European Union does not recognise Crimea's annexation and continues to condemn it as a violation of international law. EU sanctions continue to be in place against Russia as a consequence for the annexation. For the EU statement on the fifth anniversary of Crimea annexation see here.