Violating Federal Law:

It is, I am informed on the warning label, a violation of federal law to use my new bottle of Fantastik™ brand heavy-duty kitchen cleaner "in a manner inconsistent with these directions." Really?! So if I don't shake well before use, or I use on porous materials, I'm violating federal law? I've started noticing this little tagline on lots and lots of labels for lots and lots of products (I'm something of a compulsive label-reader) -- does anyone know what federal law they're talking about?