With the Staples case the court decided that mens rea was required and that mens rea would be satisfied if Staples knew (or reasonably should have known) his AR15 possessed the features that subjected it to regulation - which he did not.
The Staples case is a great precedent and I like to apply it to lots of fact patterns. We never get a free pass for not knowing the law, but, as articulated in Staples, we do get a free pass if we don't even know that the thing has the feature in question. In Staples case the government could not prove that he knew or reasonably should have known that his gun was capable of firing more than a single shot by a single function of the trigger, so the fact that it was proven that the gun could in fact do so was irrelevant.
This may come in handy as we move into the bump-stock-ban era in Florida on October 1st. Over zealous prosecutors may attempt to assert that all manner of things qualify as "bump stocks" because they allow one to fire a semi-automatic firearm faster than would be possible without the device. Using techniques like the one I call the "Glock auto finger" one can fire most semi-automatic firearms quite quickly with no device at all. Though there are many definitions of a bump stock under the new law, one of them would require the government to prove that the device in question allows one to fire the semi-automatic firearm faster than one could without it. But under Staples, not only will they have to prove that fact, they will also have to prove that the possessor knew, or reasonably should have known of that fact. Unless they can demonstrate that you have used a shot timer to time how fast you can shoot the gun with the Glock auto finger technique, and how fast you can shoot the gun with the device, it might be difficult to satisfy the principle articulated in Staples.
Personally I'd like to see a return to the days when nearly all crimes required mens rea. But I don't think it's ever going to happen. The state makes too much money and derives too much power from victimless crimes.