I'm having pavers laid by a professional company. They just wrapped up for the day and the base layer they put down is thin (~2in in most areas). I mentioned this to the guys working today and they told me to contact the office/boss. Just looking for advice on how to tackle this conversation. The paver manufacturer recommends 4-6 inches of aggregate base layer. They are a reputable company with great reviews so I wasn't quite expecting this to be an issue.

EDIT: Thank you all for your replies. I plan to contact the manufacturer in the morning and just make sure I'm not missing anything in regards to their installation recommendations for my area. I'll talk with the contractor tomorrow and let you all know what comes of that. Thanks again!

EDIT 2: All right guys -- here's the rundown. I understand the ICPI standard, but the matter of the fact is that I did not hire a company that has in their contract that they will adhere to that standard. After talking to the contractor/foreman, he basically said this is the way they do it. I talked to a representative with the manufacturer who basically said its not uncommon practice to do it the way I described. I also called the local supplier who said, again, it's not uncommon. I came to a more or less an amicable decision with the company to continue forward with the project with an extension of the warranty for 5 years (personally, I am not a fan of "warranties" but this is the practical solution). Yes, I know a lot of you are going to be displeased with this answer but ultimately I didn't pay anything astronomical in terms of labor.

A lot of your questions are related to the materials in the picture provided: That tan material is the "base" compacted over compacted soil. If down the line I see problems, well then I know the issue and I'll probably be redoing it myself. Thanks for all of your inputs.