dogs peeing on people

Question
We have two border collie / husky dogs.  They are brothers about 18 months old.  We take them to an off leash dog park every day and both behave fantastic and get along with all other dogs.  However, they have both started to pee on the legs of other dog owners during our walk, (usually when we stop to say hello or chat with other dog walkers).  The dogs just started doing this and we don't know why.  It's not all the time either, maybe just once out of every five walks, ( still very embarrassing though).  What should we do to stop the behavior?

Answer
Are they neutered?  This sounds like a typical marking behavior in a dog with a more dominant personality.  When you stop, be sure to put them in a sit or a down-it is key that they are in a position of YOU being in control.

Sorry for the delay-I had previously answered this and it is on my list again.  Something I need to address with Allexperts!