Well, it can have either meaning depending on the context. The Hindi verb "V सकना" (V being a verb root) corresponds to both "to be able to V" and "to be permitted to V".
Native Hindi speakers such as myself usually do not pay much attention to things like this.
If you do add "ko", Hindi speaker will still understand what you mean and in fact, we too frame such sentences at times.
But the solution given here is better from grammar's point of view.