This is stated in the official response of the State Fiscal Service of Ukraine to the relevant request filed by Censor.NET.
The press inquiry concerned the possibility for the vehicles having license plates issued by the 'authorities' of occupied Crimea and Sevastopol with respective 082 and 092 region codes on them to enter Ukraine
"Based on the provisions of the law, the vehicles with Russian license plates issued on the territory of the Autonomous Republic of Crimea and the city of Sevastopol are barred from crossing the administrative border between Ukraine and Crimea and pass through customs control," the document reads.
As noted, state agencies and local authorities in the occupied territories are acting solely within the powers stipulated by the Ukrainian Constitution and Laws.
The State Fiscal Service also reminded that the checkpoints defined by the Resolution of the Cabinet of Ministers of Ukraine No. 367 of June 4, 2015 must only be used to enter or leave the occupied territory.