I am no expect on the laws so I do not know what exactly is legal for eradicating them but a pipe works well.
Have a 4-5 foot pipe on the ground near your house near where they like to play.
When you come around the corner or approach a chipmunk they like to go and hide.
They will run into the pipe to hide and that's when you either cap the pipe or turn it upside down and jamb one end into the ground.
Come back a few days later problem solved.

Have fun but remember if you do shot them YOU are responsible for your bullet and where ever it ends up.

There are many ways to get rid of them that do not involve shooting them and having to worry about your bullet.

Good luck and happy hunting, trapping and or eradicating.