If, in an area where littering is illegal, I’m walking along and stop to pick up a piece of litter am I now responsible for that material? If I, say, see a piece of paper with writing on it and pick it up out of curiosity and drop it back to the ground a moment later, am I littering?
If the answer varies on location feel free to answer for wherever you can.
Minnesota Statutes 85:20(6):
No reference to how the person obtained the object, so it looks like the statute would apply. If you pick up litter, you have to carry it until you can put it into an appropriate trash can. (There are groups of volunteers who go to our parks or highways specifically to do this.)
Legally, I suppose you could hand a piece of litter to someone, and then it’s their problem – if they drop it on the ground & leave it, they could be charged with littering.
In practice, all I have ever seen a Forest Ranger do is tell the person to ‘pick up that trash and put it where it belongs’, and remind them of the littering law.