Is it legal for a government agent to order you off of your property against your will without some type of due process? Can the meter-reader for the muninciple gas company order you out of your house so they can read your gas meter? Can a police officer impound your vehicle, even though it has never left your property?
If the basis for the law has no standing against individual Rights, then that Law isn't really much of a law, is it?
Do us a favor. File a suit for a permanent injunction against your fire department, prohibiting them from entering your home unless you expressly say it is OK. In the event you are unconconcious or unavailable, they can't enter unless they've gotten approval from a court.
Next, notify your homeowner's insurance that you've taken this action in the interest of liberty. Also, advise your neighbors, so they know that if your house burns, theirs will probably be next.
Camo wearing idiot.
The authority falls to the State legislatures to regulate the actions of fire departments within their borders. In the absence of any specific statutory prohibition against firemen ordering folks out of burning buildings, one looks to the common law.
So, for example, if you wish to make the argument that the Fire Chief "tresspassed" on the man's property, or somehow "converted" it, you are out of luck.
At such times, the individual rights of property give way to the higher laws of impending necessity. Surocco v. Geary, 3 Cal. 69 (1853), 58 Am.Dec. 385 (reversing judgment in favor of owner whose house was dynamited in order to prevent the spread of fire).Despite your protestations to the contrary, what the Fire Chief was legal. (Although you could argue that the Fire Chief acted negligently--making some compensation possible. That does not appear to be the case here).
So there's your legal "basis," and it will remain the basis until it is reversed by the judiciary, or amended by the legislature. Seeing that the privilege of necessity has been around since shortly after the Norman Conquest, and the above is a textbook tort case, that appears unlikely.