I f you werent read your rights, then you can easily get your case thrown out...but thats only if you got arrested...But like Tomorrow said, sounds like they have no case so get in their face (not literaly, and be as polite as possible) and tell them they need to charge you or leave you alone, if they case is that shitty theyll usually not waste their time
And for future refernce, visit the NORML website, they break down they various laws for every state, which is VERY helpfull....