Are used trusses legal?

It probably varies between locations, but I've been told that reusing structural items like trusses is not legal in buildings occupied by the public. I know a group in Connecticut that had stockpiled a number of used trusses for a building they planned, but were told by the building inspector they could not. I've often thought that suitable shelters for display locomotives could be built cheaply using trusses from a supermarket or big-box store being dismantled. I was told, however, that no architect or engineer would sign off on such a structure because of their liability insurance. Can anyone clear this up?