Handguns could be mailed through the United States Postal Service for the first time in nearly 100 years if a proposed rule under the Trump administration takes effect. Democratic attorneys general in two dozen states sent a letter this week in opposition. In 1927, Congress passed a law barring the USPS from mailing concealable firearms unless they were from licensed dealers in an effort to curb crime. In January, the Department of Justice revisited the 1927 law, calling it unconstitutional and arguing that it violated the Second Amendment, and urged the postal service to change its regulations. The Department of Justice said that as long as Congress chooses to run a parcel service, “the Second Amendment precludes it from refusing to ship constitutionally protected firearms to and from law-abiding citizens, even if they are not licensed manufacturers or dealers.” Last month USPS proposed a new rule that would allow anyone to mail concealable firearms like pistols and revolvers.…