Kevin Kosar for the R Street Institute: By law, first-class mail is sealed against inspection, meaning that government officials may not open it without first getting a warrant from a judge. A citizen would be forgiven for imagining that this law ensures his or her mail is private, but that’s not quite true.

For one thing, other classes of mail do not have the same privacy protection as first-class mail. Additionally, thanks to GovernmentAttic.org, we now know the federal government has established three broad exceptions to first-class mail’s “sealed against inspection” protection.