Source:
http://www.recguns.com/Sources/IIF1.html" onclick="window.open(this.href);return false;
I found this with a google search...it is interesting reading.
Jason
NFA WEAPONS AND THE 4TH AMENDMENT
As to surrendering your 4th amendment (search and seizure)
rights, this is definitely true when one gets a Federal Firearms
License. The law allows the ATF to inspect your records and
inventory once every 12 months without any cause, and at any
point during the course of a bona fide criminal investigation (18
USC sec. 923(g)). They may inspect without warning during
business hours. The only modification of the above pertains to
the C&R FFL (type 03) where ATF must schedule the inspection,
(C&R FFL holders do not have business hours) and they must have
the inspection at their office nearest the C&R FFL holders
premises, if the holder so requests. ATF may look around the
licensed premises for other weapons not on your records. This
means they take the position that if your licensed premises are
your home they may search it, as part of the annual compliance
inspection. The constitutionality of the warrantless
"administrative search" of licensees provided for in the Gun
Control Act has been upheld by the US Supreme Court, see U.S. v.
Biswell, 406 U.S. 311 (1972). Biswell was partially overturned
by Congress by 1986 changes to the requirements for a warrant
under the GCA, but the administrative search provisions remain.<SNIP>