Cross Customs rulings online search system (CROSS) is a database that allows you to look for certain CBP rulings using keywords and Boolean operators.  Boolean operators are basically the tools that allow you reduce your search results, which include the words AND, OR, NEAR.  Other useful information when searching for a ruling is that punctuations such as periods, colon, semicolon, and commas will be disregarded.      
The following link below will take you directly to the Cross ruling website:
http://rulings.cbp.gov/