The FMVSS governs the sale and manufacture of vehicles in the United States. However, what is legal to own and operate is governed by your particular state's vehicle code. Blinking third brake lights are legal to operate in many states. What is typically restricted is the rate and total number of times the light may blink. As an example my state's vehicle code reads:
25251.5(c)
Any stoplamp or supplemental stoplamp required or permitted by Section 24603 may be equipped so as to flash not more than four times within the first four seconds after actuation by application of the brakes.
So basically the dealership can't legally sell it pre-installed, but they can sell you the mod and install it after the sale if it's legal to use in your area.
Gotta love Kalifornia. That regulation is actually a violation. See my bolding below
From the
CATO institute:
Can a state impede federal authorities from enforcing their own law if the state deems the law to be unconstitutional? The answer is “No,” although more radical nullification proponents would disagree. They point to the Kentucky and Virginia Resolutions of 1798 and 1799, in which Thomas Jefferson and James Madison asserted a state’s right to nullify the Alien and Sedition Acts.
But consider those resolutions in context: Jefferson and Madison had argued that the states must have the final word because the Constitution had not expressly established an ultimate authority on constitutional matters.
Four years later in Marbury v. Madison, Chief Justice John Marshall resolved that oversight. He wrote: “It is emphatically the province and duty of the judicial department to say what the law is.” Since then, instead of 50 individual states effecting their own views regarding constitutionality, we have one Supreme Court establishing a uniform rule for the entire nation.
The Framers concurred. In Federalist 78, Alexander Hamilton had written: “\ limited constitution … can be preserved in practice no other way than through the medium of courts of justice, whose duty it must be to declare all acts contrary to the manifest tenor of the constitution void.” Madison shared that view. He wrote: “(I)ndependent tribunals … will be an impenetrable bulwark against every assumption of power in the legislative or executive.”
Even before Marbury, the Virginia General Assembly had passed Madison’s Report of 1800. It acknowledged that states can declare federal laws unconstitutional; but the declaration would have no legal effect unless the courts agreed. Here’s what Madison wrote: State “declarations … are expressions of opinion, (intended only for) exciting reflection. The expositions of the judiciary, on the other hand, are carried into immediate effect.”
Madison also published Notes on Nullification in 1834. There,
he wrote that an individual state cannot unilaterally invalidate a federal law. That process requires collective action by the states. Similarly, Jefferson’s Kentucky Resolutions had described nullification as an act by “the several states” that formed the Constitution.
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While no state can create a regulation that overrides a federal regulation, they can decide not to inspect for, or enforce, a certain regulation.
Accordingly, a state can say "we don't care about third brake lights so we won't see if they are working during inspection" but they can't legally say "the brake light can flash"
This actually makes sense. If a state would create a law (a flashing brake light for example) then a California driver could get ticketed while driving in a state that enforces the FMVSS.
California is, in this case, violating the law.
