Did some of the Seven Warlords commit acts that would reasonably constitute treason against the World Government during the Marineford War? Due to the legal definition of treason in my country, I will only be considering acts committed during the war itself, so turning large quantities of Marines to stone during the Amazon Lily arc and on the way to Impel Down will be ignored.
Boa Hancock prevented Pacifistas and Marines from attacking enemy combatant Monkey D. Luffy on numerous occasions. She has also injured and partially petrified some Marine soldiers via indiscriminate attacks that also affected parts of the Whitebeard Pirates if I remember correctly. At one point when Luffy was running up a bridge to the platform Ace was on with Garp standing in front of him, Hancock prevented some Marines from taking aim at Luffy. It’s been a while since I watched the episode so I don’t remember if she simply blocked the Marines from aiming, outright attacked them, or something else. She has also outright destroyed Pacifistas, which were being used as Marine weapons in the war.
If I remember correctly (it’s been an even longer while since I’ve seen that episode and I can’t check right now since my Netflix isn’t working), there’s a scene where Gecko Moria has several Marine soldiers’ shadows in his hand for use in animating zombies. This is occurring in direct sunlight. If someone having lost their shadow from Moria’s ability is exposed to direct sunlight, they begin to burn to death, and Moria should know this. We thus have him commit an act that he should know will result in several Marine deaths.
Blackbeard arrives at Marineford with hostile intentions accompanied by five of the world’s most heinous criminals fresh out of prison (four of which his crew personally freed), effectively invading the Marine HQ. He also contributes further to the damage to Marineford that had been done by Whitebeard, and participated in direct combat against Sengoku.
Jinbe is literally a full-fledged enemy combatant, and his purpose is to assist other enemy combatants in preventing the Marines from achieving their objective of executing Portgas D. Ace.