It's a violation of Federal law for firearms to be in an unsecure container while in checked baggage. If someone removed the locks at any point between the time you checked-in the case and the time you claimed it from baggage, they committed a felony. The TSA does not trump Federal law in that regard. When the TSA passed down the assinine edict of leaving checked baggage unlocked, I immediately sent a letter to the TSA to ask specifically about checked firearms, pointing out that their "request" was contrary to Federal law with regards to firearms in checked baggage. The TSA's response was that the applicable Federal laws overrule their policy and firearms should be secured in a locked container as the law calls for. The TSA's own website states "Federal regulations prohibit unlocked gun cases (or cases with broken locks) on aircraft". It also states "If you are not present and the security officer must open the container, we or the airline will make a reasonable effort to contact you. If we can't contact you, the container will not be placed on the plane."
If someone removed the locks from my case and allowed my firearms to be left unsecured, I'd raise one hell of a dust cloud with the TSA. You can bet that if you had left your case unsecured the TSA would likely have taken away your guns and would be looking to put you in prison: "We and other authorities strictly enforce these regulations. Violations can result in criminal prosecution and civil penalties of up to $7,500 per violation".
To my knowledge, there is nothing that defines or mandates an "approved" case. The regulations state "hard sided container". Period. If someone tries to tell you that your container doesn't meet a certain specification, they're blowing smoke. However, I personally wouldn't use a Glock factory case as a standalone container. I recommend a Hardigg or Pelican case for a standalone gun case to be used as checked baggage. I also recommend that a second set of padlocks (keyed the same as the ones on the case) be kept inside the case so that you can use them in the event that some TSA jackass cuts the locks off of your case. Otherwise, you're left with no locks and potentially a big hassle.
You can read the regulations here: http://www.tsa.dhs.gov/travelers/airtravel...orial_1666.shtm