Are security checkpoints illegal inside the US?

take this for example: http://www.liveleak.com/view?i=133_12103...

@Return of Bite My Shiny Metal:
On whose authority?

As Bender (Sorry, it's just easier to say Bender instead of typing out Bite My Shiny Metal...) pointed out, it is perfectly legal for them to set up these checkpoints. The idea of checkpoints was challenged years ago when they started using them to set up sobriety checkpoints. The argument was made that police needed probable cause to pull you over and check for sobriety. The counter argument was made that drunk driving was so commonplace and prevalent on the roads that this constituted probable cause. The courts agreed.
Police are allowed to stop people when they have probable cause and, in the case of the checkpoint you posted, they would get their probable cause from the argument that illegal immigration is prevalent and these immigrants are likely to be found traveling roads near our border.

Since you seem to really want the legal citation, this issue was decided in a 6-3 vote by the Supreme Court in 1990 in the case Michigan Dept. of State Police v. Sitz.

UPDATE: No, I'm not saying probable cause = everyday activity. The COURT is saying that the high probability that cars passing a certain point will be driving drunk counts as probable cause. Even that is a simplification, and I'm not saying I agree with it. I'm simply passing along what the court said. I'll include a link to information on the Supreme Court decision.

http://en.wikipedia.org/wiki/Michigan_De...

It's a tricky issue...
The constitution makes it clear that the intent was for police actions to be made only under probable cause. However that applies to apprehensions, searches and prosecutions.
A traffick checkpoint is considered to fall under the guidelines of a 'detention' which requires less than probable cause. Probable cause for a search found subsequent ot a detention is legal.
So, they can't stop you and search your vehicle arbitrarily, but if they stop you and you appear intoxicated, or anything is in plain view then they have probable cause to search, and make an apprehension if appropriate.
Yes, it's skirting the intent of the constitution a bit, but it is legal.

No. They have a legitimate purpose which is to look for illegal aliens. The city police are constantly setting up drunk driving checkpoints in big cites. I've also seen them set up for the purpose of verifying registration, drivers license and proof of insurance, even though I believe the underlying reason was to catch drunk drivers.

I was once stopped in North Carolina on US Route 1 where I was asked to produce my drivers license, registration and proof of insurance. I was told that they were most likely looking for drug runners. All I know is that it took me 2 minutes and I was on my way.

Edit:
Governments at every level possess that authority. It comes under protecting the health, welfare, safety and security of the public.

No..

no