The decree came after Russia announced that four Ukrainian regions would be annexed by Moscow. The Ukrainian Security and Defense Council, chaired by Zelensky, called the annexation a violation of international law.
In the first weeks after the invasion, there were still talks between representatives of the two camps. However, Moscow imposed unacceptable conditions for Kiev to take those negotiations down to the presidential level. As far as Kiev is concerned, negotiations can now only start after a complete withdrawal of Russian troops.