Green MP Caroline Lucas told the court she felt it was important to protest about fracking to prevent the UK from being locked into using more fossil fuels.
Ms Lucas said: "I'm haunted by the idea that my children and my children's children will turn round to me and say, 'What did you do about this overwhelming threat?'"
Her co-defendants were also cleared of both charges against them. They were Josef Dobraszczyk, 22, from Bristol; Ruth Jarman, 50, from Hook, Hampshire; Sheila Menon, 42, from north east London; and Ruth Potts, 39, from Totnes, Devon.
More top news
Winter: it's not over yet
Supporters are taking part in a march to the King Power stadium following the sacking of their Premier League winning manager.
Sir John rejected the PM's Brexit vision as "unreal and over-optimistic" as he accused negotiators of "souring" the atmosphere for talks.