Is it illegal to help remove invasive plants at public parks?

There is a highly invasive vine in a favorite park in my neighborhood. This particular vine is considered highly invasive in many states along the east coast including mine. I saw a young oak tree being smothered by this invasive vine. I pulled and cut some of the vines using a plant shear to free up the tree. About an hour later, a man and woman confronted me. The man asked if I worked for the county, I said no. He became very angry with me and said “No cutting, no pulling!!!” He then told me if someone were to report me to police, the police would arrive immediately and have me arrested. The woman was calmer and told me “This is a park, you can’t do that”. I told them that the vine is highly invasive in the state. They told me it doesn’t matter, the police don’t care I will be arrested. I offered to clean up and leave. The woman said Thank you. As I was leaving the man continued to stare at me angrily. I’ve seen articles of people/groups in my home state and other states in the east coast helping to remove invasive plant species. I don’t understand, is it illegal to help remove/trim back highly invasive vines that threaten the ecosystem at your local park? Is this really something the police will arrest you right on the spot and press charges? What could they possible charge you with? I am doing this in the daytime and helping to keep these invasive vines under control and protect the native plants.