your job as new boss is to teach. no gain is to be had by anything but tactful delivery of the message (well documented, signed, dated, witnessed, and signed by employee – OF COURSE) and then the second time it happens, again – have them witness and sign the first one (already signed – yes again)- and sign something again that they again violated said law.

SO…. in this case, it may feel tactless, but if you have to do it in the course of business, do it softly and with a big documentation list…