I'm sorry no one has answered you sooner. I don't know the law about digging native plants here, but I'm sure if you ask the property owners they'd let you dig all the dewberries you want. I know I would. However--someone surely has selected plants with better-tasting berries, which I would recommend looking for, as the ones I've sampled have pretty tasteless ones. Or, on the other hand, be patient. I never planted dewberries, but I spend a great deal of my precious time outdoors digging up the blankety-blanks the birds bring in all over. Really gotta get me some gloves. I hate gloves,