Colorado Magazine Ban

 Colorado's governor has signed new gun-control legislation, that require background checks for all private gun sales and a ban on large capacity detachable magazines. I myself have not actually read the legislation so I can only go on whats in the news but the magazine ban would seem rather ineffectual 

As I understand it you can keep any mags you have. But you cant bring any new ones into the State of Colorado.

How can that possibly work? Last time I looked you don't get inspected when you drive into Colorado so who would know you are bringing in magazines. And even if you did get stopped how would the police know you did not already have the mags before the ban came into effect. Mags don't have dates printed on them. So you would just say they were old mags. And as most people who are interested in guns now know we are starting to see people printing mags on 3D printers. How would the police know if you printed the mag before or after the ban?

I also noticed that they chose over 15 rounds as the definition of a large capacity detachable magazine. So what is the point of that? Are they saying its OK to shoot 15 people but 16 is over the line. And I guess the Government is not aware of the fact that you can tape mags together so the next one is handy for a quick mag change.

I did a quick test and it only takes my wife 5.9 seconds to do a mag change on my AR-15 and she is not an AR shooter. It was her first time with an AR and she was already fast. With a little practice I suspect anyone could do it in under 3 seconds. So I ask whats the point of limiting the mag to 15 ?

I just don't see the point.