The opinion came in response to questions raised by state Rep. Jason Overstreet in December.
Ferguson said that whether a foreign conviction is comparable to a Washington state felony is determined on a case-by-case basis. But when the determination is made that the crimes are comparable, those who issue such licenses - either a sheriff's office or police office - are prohibited from issuing a concealed pistol license to such applicants.
In his request, Overstreet cited the case of a nonresident, dual American and Canadian citizen who currently resides in Canada. The person was denied a concealed pistol license from the city of Sumas but received one from San Juan County.
The person had no convictions in Washington state or other U.S. states, but had convictions in Canada, including one for assault with a firearm. Ferguson wrote that a similar conviction in Washington state would disqualify the person from obtaining a concealed pistol license.
"An individual who has been convicted in a foreign country of a crime that is comparable to a felony under Washington law is prohibited from possessing a firearm in Washington and, accordingly, is ineligible for a concealed pistol license," the opinion reads.
Ferguson noted that current state law regulating the use and purchase of firearms specifically defines felony and serious offense to include any federal or out-of-state conviction that is comparable to a felony or serious offense under Washington law.
Ferguson cited a 1998 case, State v. Morley, in which the Washington Supreme Court decided that a military court martial could be included as part of a defendant's criminal history during sentencing.
"In so deciding, the court broadly interpreted the term 'or elsewhere' to include 'all foreign convictions, whether from other state courts, federal courts, military courts, and perhaps even courts in foreign countries,'" Ferguson wrote.
Ferguson wrote "the Washington Supreme Court's discussion in Morley strongly suggests that the plain meaning of 'elsewhere' and 'out-of-state' include foreign jurisdictions."
A message left with Overstreet's office was not immediately returned Tuesday.