Call the HOA to confirm they are tresspassing.

Then call the law if so.

I agree, call the police.

Then, after you call the police call your local game warden.

Then, after you call the police and game warden call your HO Assn. president and file a formal, written complaint.

Other than throwing nails under their tires while they are fishing I don't have any other suggestions other than to ask them to leave but that may place you in a dangerous situation.

I like the nails.  ;D

Unfortunatley now days people are getting shot for a lot less than even a friendly confrontation.  It's in the news daily.  If you're compelled to act at all, call authorities.  They are better equipted for them kind of conversations.

Years ago I was driving past some of our family property during deer hunting, when I noticed 2 pieces of orange that didn't belong.  When I pulled in and went to talk with them, before I knew it I was surrounded by about 12 pieces of orange telling me that my property wasn't posted so therefore was their's to hunt.  I agreed, and was more than happy to get the hell out of there.  Went home and called the warden with a tag number, and promised myself never again.  JMO