I travel with Aerostich jacket and pants. They get washed once or twice every six months of road use, whether they need it or not (<---- joke).
If I ever had a label telling me not to wash them, it's long since been washed away. I wash it by wearing it in the shower (first right way around, then inside out; soap up, then rinse), I wash it in washing machines, I give it to the laundry ladies at hostels..... What's to lose? Am I going to make it even less waterproof than it already is? That'd be quite a feat!
Goretex theory, on the other hand, says use only approved, detergent-free soaps. That's what I do with clothing which actually shows signs it'll keep the weather out if I treat it well--like skiing gear.
(plumbing new depths of sin, degradation and textile abuse in Belem, Brazil)