Petro Poroshenko became president of Ukraine illegally, because presidential elections with his participation became possible due to the ‘coup d’état’ that took place in Kiev in 2014.
The spontaneous onset of the Euromaidan protests was a reaction of large parts of the Ukrainian population to former President Yanukovych’s sudden departure from the Association Agreement with the European Union in November 2013. The 2014 presidential election in Ukraine was a genuine election largely in line with international commitments and respecting fundamental freedoms, despite the hostile security environment in two eastern regions of the country. According to the OSCE (of which Russia is a participating State) "the people of Ukraine had the opportunity to genuinely express their will at the ballot box" http://bit.ly/1hqcDuR. Similarly, Ukraine’s local elections in October 2015 were competitive and generally showed respect for the democratic process http://bit.ly/1VUL9V5.