Dog Muzzle or not?

I've just booked a ferry crossing Poole to Cherbourg and will be taking my two dogs.  In the blurb it says dogs must be muzzled when outside the car.  The only time they will be oustide the car is at check in on the return trip.  I didn't have them muzzled on the Euro tunnel crossing we did with them last year. Is it different for ferry crossings?   Can experienced ferry travellers with dogs advise me please?!?