Pass a law that mandates gas storage facilities be filled by winter.

Only, what are you going to fill these storage facilties with? If Vladimir Putin turns off the gas, I mean. Oktoberfest beer?

Germany approves law mandating full gas storage before winter – The Bundestag lower house on Friday approved legislation requiring Germany’s privately-operated gas storage facilities to be full at the start of the next winter, to try to avert shortages in the event of a halt in Russian gas imports.