That is going to depend on where they send you. Labor Ready might not have a problem with it but their client might. And their client might not say anything to you but instead ask Labor Ready to not send you out anymore. Which in turn may cause Labor Ready to send you less paying and fewer jobs. Just my experience as a contractor. Easiest thing is to ask Labor Ready what their policy is and if they see any problems with it. Or better yet ready any new hire paperwork as most employers will state their rules regarding weapons in the workplace.
Unfortunately my contracts require me to work for various government agencies that might not be so understanding. Other times if I know the customer/client more personally I can get away with it even though it looks extremely funny watching me run around with a gun and a laptop tearing apart computers lol.