Last week, Sen. Al Franken, D-Minn., was one of four U.S. senators to sign a letter asking social networking website Facebook to repeal recent changes to its release-of-information policies.

Members of Congress and Facebook users alike need to understand that this website is not a free and open public forum. It is a business, and their business model is to share users’ consensually offered personal information in order to generate, at the minimum, advertising revenue. Asking Facebook to respect its users’ privacy is asking them to waive the site’s cost of admission.

More importantly, if Franken and his colleagues are serious about protecting their constituents’ privacy — and they should be — they can work to establish a firm legal foundation for a national right to privacy.

Privacy isn’t technically considered a right in the United States. Its few protections are drawn from a convoluted series of court precedents based on a patchwork of clauses from various constitutional amendments. This all-too-tenuous penumbra right (one “cast by the shadow” of the Constitution) is so weak, apparently, that concerned senators’ first recourse in defense of privacy is to write obsequious letters to CEOs.

Facebook’s recent policy change only highlights the need for a right to privacy that has firm constitutional footing. The past decade’s dramatic technological leaps in communications and surveillance pose a threat to Americans’ privacy that the country’s founders could never have dreamed of.

Citizens, for their part, need privacy protection not only from corporate forces but from their own government. The (noncorporate) people of this nation must demand the right to privacy.