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Portable Halon extinguishers made before 1995 are legal for use.
Aircraft are still allowed to use Halon.
It is illegal to release holon into the environment except for use in
"emergency" fires (ie it is illegal to use for "training" purposes)

This, of course, varies with the country.

IMHO, Halon is not the ideal extinguishing agent for most aircraft fires,
especially in-flight. In order for Halon to be effective, it must be applied
to the fire before anything in the vicinity of the flammable gases becomes
heated to the ignition temperature of the gas, otherwise the fire will
re-ignite as soon as the concentration of the Halon drops below the
percentage needed to interfere with combustion.

Establishing and maintaining the required concentration of Halon is
difficult, if not impossible, in an open space. Even closed environments
such as sealed buildings are difficult to permeate. It is likely impossible
under an aircraft cowling when the plane is moving.

One needs to understand the process by which Halon inhibits fire. The fuel
(usually carbon-based material) has a greater affinity for the Halogens
(Chlorine, Fluorine, Bromine & Iodine) that it does for Oxygen. In the
presence of both Oxygen and a Halon, the fuel will "choose" to combine with
the Halon without the evolution of heat and light - what we call "Fire". If
sufficient Halon is available, all the fuel will combine with the Halon and
the fire will go out.

If the Halon is removed and there is still a source of ignition, the fire
will take up right where it left off.

If you've got a cabin fire, that's a horse of a different smell.

Rich S.