the one thing that definitely can have legal repercussions is conflict of interest, eg if you work two jobs in two competing companies, both will sue you if they ever find out
that and NDA and ownership to work you complete during time that you're supposed to be working for them. the expectation usually is if you're billing them for a certain number of hours, you are working for them - if you're paid a salary then that's a non-issue as long as you complete your assigned work. that said Ibrown town and this is just what i vaguely remember from reading random stuff on the internet over the years
i suggest looking at your employment contract to confirm whether or not they can/will take legal action, im pretty sure most companies have a stipulation on this somewhere.