I was about to tell you that when you go into international waters and return you are required to report back in. Then I remembered something that happened about two years ago.
I was crew on a foreign flagged yacht with three foriegn crew. We took the boat offshore to transfer ownership and even photographed the GPS to prove that we were not in US waters. We had three lawyers on board. When we came back we went straight to our slip without ever checking back in. In retrospect this seems wrong.
In another case I did a race last winter from SanDiego, down around the Rosarito Beach Bouy in Mexico and back. The customs guys did a bulk pre check in with all of the skippers the day before. Again we had several foriegn crew, and not an issue but the precheck was required or we sould have had to clear in after leaving US waters.
So...I'm not 100% sure what the rules are. I Canada, you definitely have to check in if you leave Canadian waters. I'm pretty sure US has the same rules.