I retired from a local agency in Louisiana and moved to Texas in 1998. Last year I researched concealed carry and found LEOSA, Public Law 108-277. It is codified as 18 U.S. Code 926B (qualified law enforcement officers) and 926C (qualified retired law enforcement officers).
Texas is very accommodating. They have a process with forms in place to show proper weapons qualification. If the retiree desires upon successful weapons qualification, he can complete an official Texas Commission on Law Enforcement Officers Standards and Education form and mail it in with a $25 fee. A qualification card with photo is issued and good for one year from date of qualification. Renewal is the same cost and process.
However, it is not necessary to get the card. A signed notarized affidavit that is part of the form mentioned above will suffice since 18 U.S. Code 926B and 18 U.S. Code 926C does not specify such a ID card as a necessity, just proof of weapons qualification.
This is for all retired local, state, and federal officers.
The Word docment form can be found under "Retired Federal Firearms Identification Card" in this URL,
http://www.tcleose.state.tx.us/content/publications.cfm . Although it states Retired "Federal Firearms..." it is for "Retired Federal or Out-of-State Officer Firearms Certificate"