If the US Govt patents something, what are a private citizens rights to that patent?

I understand that the US govt is not supposed to compete with private enterprises. But they patent things frequently. The National Labs for instance have quite a few patents. If I were interested in commercializing a process that involves one of these patents, what rights to that patent do I have as a private citizen?I have a hard time believing the first two answers are correct. If so, then the govt is likely sitting on quite a few patents that were paid for by tax payers. If they are not being used, then the govt is effectively impeeding its own economy.