Of course. And any contract flying we may do on our "off" time has to be reported to the company. This doesn't include any pleasure flying, but flying when we're earning extra money.
Personally, I have never done any contract work in my off time and only know a handful of pilots who do. I want the protections of a union just in case I do something stupid. For example, if I accidentally have an incursion or an incident, I want to be able to have the protections of ASAP which wouldn't happen flying outside of the company.
Ever hear of NASA report