[mikeash]

See the Better Business Bureau for another example of this.

However, I don't think it's the fault of "the." Nobody thinks The New York Times or The Washington Post are government entities, for example.

[scarmig]

It seems like the "of" does it more than anything. It parallels organizations like "Department of Defense" and "Federal Bureau of Investigation": some generic noun to represent that it's an organization of people, "of," and then an abstract noun that gives the organization a purview that's universal or total in scope. Most organizations that have the audacity to do this have a monopoly on the use of force behind them.

The CoC, of course, is itself in the business of government: trade its governmental access and leverage to businesses in exchange for large cash grants.

[cmdrfred]

There are multiple chambers of commerce [centralpachamber.com, njchamber.com] so perhaps the intent is to differentiate them?