Crimea was not "returned" to Russia, it was illegally annexed in a military operation. A recurring pro-Kremlin disinformation narrative about the illegal annexation of Crimea.
Crimea is a part of Ukraine and was illegally annexed by Russia. In 2014, with Russian troops controlling the area, a referendum was hastily organised, illegitimate under international law. The peninsula was illegally annexed and brought under Russian territorial control.
No international body recognises the so-called referendum.
A year after the illegal “return”, Russian President Vladimir Putin admitted that the plan to annex Crimea was ordered weeks before the so-called referendum.
Sanctions were first introduced in June 2014 in response to the attempts to deliberately undermine Ukraine’s territorial integrity and destabilise the country. Other EU measures in place in response to the crisis in Ukraine include economic sanctions targeting specific sectors of the Russian economy and individual restrictive measures. For the EU's statement on the sixth anniversary of Crimea annexation see here. The sanctions were renewed on 10 September 2020 for a further 6 months until 15 March 2021.
Read similar claims such as Crimea’s reunification with Russia was legal, or that historically Crimea was a Russian land, and that Crimea became part of Russia after the events of 2014 in Ukraine.