Actually the cop will chase you, i dont think its a law anymore that they cant, by going that fast your putting you and other people in danger so they will stop you! But its mostly for people they ...

your missing the point, they can chase all they want, but there cars dont do to well at 120+ speeds, id like to see them take a turn and those speeds... bikes and sports cars can, there's well have...

So you dont think they have fast cop cars, bikes even, heck they have helicoptors. If they wanna chase you they will.