Well yes, there are times where it legal to take someones possessions/money such as if they owe a debt or have a legal judgement against them. In that case it could mean for instance sheriff deputies showing up at your house with guns and taking things in a manner that would be legal and not be considered robbery. When it becomes one thing or another is going to depend on your position on other things, there is a legal answer for when it becomes robbery/murder but also moral answers. I am for example a moral realist, so my answer to that would be different than someone who was a moral relativist.