[Gordongekko909]

"The US Constitution reserves to the federal government the right to establish post offices and post roads."

It's a RIGHT, not a MANDATE. The Constitution does not require a Post Office. Privatizing the USPS would be completely Constitutional.

[muawiyah]

It would undoubtedly be Constitutional for CONGRESS to establish post offices however it wishes. It would be Un-Constitutional for a State Government to do so.

The dispute here is between State authority and Federal authority.

Private parties can, of course, provide their very own mail service ~ and do so. What they cannot do is offer those services for sale outside of their internal structures without permission.

This is well established law.