Is the potential for autonomous transboundary movement by certain types of gene drive-modified mosquitoes unprecedented?

No. There are established precedents for autonomous transboundary movement. Classical biological control, for example in which non-native insects are released for the purpose of reducing or eliminating an insect of economic or public health importance, has been practiced for well over a century. Biological control agents are expected to become permanently established over large areas irrespective of political borders. The International Plant Protection Convention has created guidelines for the export, shipment, import and release of biological control agents that describe the responsibilities of governments and importers. Some wildlife vaccination programs seek to make non-hereditary genetic modifications in free-ranging species such as racoon and fox to reduce the risk of rabies transmission to people. And the possibility for autonomous dispersal, for example of pollen or spores, also has been a consideration for GM crops.

For more information:
https://www.ippc.int/en/publications/guidelines-export-shipment-import-and-release-biological-control-agents-and-other/