FYI-  For what it's worth, I just called the US  Customs Service and they said that I was found ***ineligible*** on the initial pre-screening packet for an entry-level 1811 position, because I had 'inadvertently' marked 'no'  to the question   " Do you agree to submit to a polygraph examination, if required". Key word- if required!!!   I thought I had answered 'yes'.     I am going to re-submit a new application today noting 'yes' I agree to submit to one, but my point is that they are declining people who just say "no" to the 'possibility' of submitting to a polygraph.
 
I heard this verbally; they said that they would send out a written denial based on my answer of 'no', in a short time. I'd like to get a copy of this in writing. But that could take forever!

Just thought you should all know of this situation.

To answer your question:
The following is from the new USCS Entry Level (GS 5/7/9 Criminal Investigator applicant booklet explicitly  states:

"Are you willing to undergo a background investigation, which may include the administration of a polygraph examination?"


The vacancy announcement (e.g.  INVSC/00-097AGO, etc. )for current gov't employees, and current USCS employees explicitly states:

"POLYGRAPH EXAMINATION: Tentative selectee may be subject to successful completion of a polygraph examination".

As the word 'may' is included in both statements, I'm am not sure if a poly is "required", but they are leaving themselves an out and  reserving the right to test - if they so choose.  But as I found out, if you say that you don't agree to even the  "possibility" {emphasis added} of submitting to a poly', you are dropped from the applicant process right then and there!!!!!   

In the past USCS did not require the poly.  Seems that the USCS is acting just like ATF (who just jumped on the poly bandwagon), in that they (USCS)are just now requiring the poly for new agents.   At this rate, pretty soon the USMS, Border Patrol, NCIS,  and the OIG's will soon all require a poly!!!!!!!!!!!!!