Picking fruit from a tree owned be a non-religious Jew
Question
May I pick fruit from a tree that isn't mine? The tree in question is not in a private yard, rather on a public road and it's the shemitah year. The problem is that the owner of the tree is not religious, is unaware of the halachah, and in any case is not willing to declare the fruit of the tree ownerless.
Answer
This question was disputed by the Torah giants in past generations. According to the Beit Yosef and Mabit, it seems that if the owner of the tree fails to relinquish ownership of the tree's fruits, it is improper to take them against his will. It is improper to do things—even if halachically permissible—if the owner is unaware of his obligation. Furthermore, there are posekim who require asking permission to pick fruit even from trees that were declared hefker. So it is certainly improper to take them without permission.
Question
I have a tree that is full of fruit, Baruch Hashem. Am I allowed to pick a big bag's worth of fruit and give it as a gift to a friend?
Answer
You are supposed to relinquish ownership of the fruit of your tree. Just like anyone else, you are allowed to pick a week's worth of fruit and even give it to a friend.