Murray Rothbard, revolutionary anarchist and socialist, put it best: All Power to the Soviets. No. Really.
The argument goes that only justly acquired, through homesteading or trade from those who justly acquired it, property can be held to the standards of property. Thus, if someone steals unjustly acquired property, that person has done nothing wrong. As a result, property that has been unjustly acquired is not property at all.
Now, what does it mean if it isn't property at all? Well, it means the property is ripe for homesteading, and the only ones who are mixing their labor with the "property" in the workplace are the workers. Thus, the workers, not the capitalists, are the just owners.
All Power to the Soviets, indeed.