I know this topic is almost a year old, but I thought I would add my opinion for future permies browsing old topics (such as myself). It looks a lot like what my parents have on top of their root cellar. In the same family as the black and honey locust, but a different type. Theirs is technically classified as a shrub. If you want it gone, keep it mowed down. The ones on top of my folks' root cellar is where the lawn mower can't reach. I don't know how it was introduced, but It's been there for 20 years now. The oldest and largest is about 10ft tall with a trunk diameter of approx 4 1/2 inches. Theirs spread by roots, and once established, the root system is damn near impossible to kill. Its branches I would call "fuzzy" but there are thorns on the older and more developed parts. Flowers are pink and look similar to pea blossoms.
I don't know if that's what plant that is, but it's a possibility. If you want it gone, I recommend keeping it cut down as if your life depended on it. It is prolific. Or you could turn it into a resource. The bees LOVE the flowers, and the wood can but put to use in some way.
Old topic I know~
I've had these in my yard; short of it, after a good rain I'd give a wiggle jiggle pull and near all of root would come out. Now I really don't have any.
As said mowing didn't really get rid of them. Tips me hat~