The pair climbed on to the top of Plymouth's Crown and County Court at about 0600 BST on Tuesday.
Dressed as Spiderman and Batman, Jolly Stanesby, from Ivybridge and Gary Swain, from Crewkerne, Somerset are members of Fathers 4 Justice.
Police cordoned off the front of the court, but the day's proceedings were not affected.
Mr Stanesby said he was protesting against alleged injustices in child custody hearings.
"The family courts are held in secret so nobody finds these things out.