49 CFR § 1542.207 - Access control systems.
(1) Ensure that only those individuals authorized to have unescorted access to the secured area are able to gain entry;
(b)Alternative systems.TSA may approve an amendment to a security program that provides alternative measures that provide an overall level of security equal to that which would be provided by the measures described in paragraph (a) of this section.
(d)Secondary access media. An airport operator may issue a second access medium to an individual who has unescorted access to secured areas or the AOA, but is temporarily not in possession of the original access medium, if the airport operator follows measures and procedures in the security program that -
(1) Verifies the authorization of the individual to have unescorted access to secured areas or AOAs;
(2) Restricts the time period of entry with the second access medium;
(3) Retrieves the second access medium when expired;
(4) Deactivates or invalidates the original access medium until the individual returns the second access medium; and
(5) Provides that any second access media that is also used as identification media meet the criteria of § 1542.211(b).