I direct your attention to this thread which bears on your question. Let me also remind you that while we tend to take all of Rand’s writings as interchangeable without regard for time context, Rand started writing The Fountainhead in the mid-30’s whereas her non-fiction works built on Atlas Shrugged decades later. The question of what you call the act is irrelevant, the right question is “Was the act morally proper?”. Rand is very clear in her later philosophical writings that in a civilized society, man cedes his right to defensive force to the government, and a government holds a legal monopoly on the use of physical force. Roark should have sought forceful government intervention, as required by law.
There are numerous imaginary scenarios that could be applied to the effect that this principle does not apply. For instance, one could conclude that Roark was not living in a civilized society, he was living in the wild, wild west of Medieval Mongolia where dog eats dog. The same can be said about all stages in US history, that we are not and have not ever been an Objectivist utopia, yet it remains invalid to argue “Because society is imperfect, all forms of force are sanctioned”. A more realistic argument would be based on the reality of civil judgments and breach of contract – I pointed this out earlier. A money judgment would not result in justice, only removal of the offending object would.
It is not obvious to me whose property rights were violated, since we are dealing with a subcontract. Keating breached his contract with Roark, as well as with Cortland (the contract was for a building, not a pile of rubble). Roark’s action was against Keating, who remains responsible for the creation of the final building. If we take Cortland out of the picture, Keating had to right to the building that he created, but this is an extrajudicial act of force, of taking the law into your own hands. The law is not a suicide pact. My opinion is that the trial outcome is as implausible, in the real world, as the alternative where the court orders the demolition of the building.
The issue that is not clearly worked out in Rand’s philosophy is under what circumstances may we properly assume that we are not living in a civilized society – when is it proper to ignore the law?
The public safety regulation argument is a red herring. There is no evdence that blowing up the building threatened anyone’s safety. FYI, no legislative solution would have been valid (it would have at most created an avenue for blowing up future buildings). The courts could have insisted on specific performance, but that is a purely surreal legal possibility, not one that actually exists. Also, “rights” and “force” are not the same thing (or, exact opposites), your argument should be focused on what Rand said about an individual using force. Roark’s rights were patently violated. Roark used force in response to Keating forcefully violating his rights. It is correct that individuals do not have the right to retaliatory force.