currently work for an FAA Repair Station. I'm not an A&P as I'm in marketing, but I am very familiar with FARS etc. everything that has been noted by prior posters is correct regarding airworthiness compliance, but I'd like to add one other point of interest.

all of our A&P's undergo mandated random drug tests. We just had the local agency that administers them in yesterday as a matter of fact. They do about 10% of our group every time (we have about 40-45 hands-on folks).

don't know what TSA's drug policy is as far as testing. probably have to pass one prior to employment. doubt if they are tested subsequently. maybe one of our TSO's can answer that.

either way if the TSO's are even so much as touching a part they are breaking the law.