Not terrorism. Since the pipeline was a Russian economic asset, it was a legitimate military target for Ukraine as a recognized belligerent against Russia. That being so, the German criminal charges should be dismissed because they contravene the immunity from criminal prosecution enjoyed by combatant personnel engaged in military operations.
It was in Danish waters so it is technically an act of war against Denmark
If the pipelines are a legitimate military target why does Ukraine still allow the passage of Russian natural gas through Ukraine?
https://apnews.com/article/russia-ukraine-war-natural-gas-f9f00df7195d01404f8cb2a43152a8b1
So if a Russian blows up the Ukrainian embassy in New York, the Russian should not face criminal charges, because the 2 countries are engaged in a war? (For purposes of this question, ignore the fact the embassy is considered Ukrainian soil)
So it wasn't a valid military target since the collateral damage to an ally was not worth the damage to Russia since Russia is now just shipping its oil via different routes.