Under what legal standing can after-hours ground access to an airplane be forbidden? (USA-specific only) This came up when a friend was unable to access his airplane because the security guard refused to open the gate. It was a mountain flight in a small plane, and so a timely departure was urgent for safety. The security guard didn't have a reason not to let the pilot access his plane, he simply felt he didn't have the authority to make that decision.
In the end, he was only delayed 45 minutes and didn't miss his weather window. But after I heard the story, it got me thinking what we should do when confronted with this situation, especially if the delay will cause severe consequences (missing a weather window, for instance).
In the US, under what normal conditions can a pilot be forbidden access to her/his plane, and what are the legal justifications for that? I have flown out of the obnoxious KBED and so am familiar with heavy-handed escorts, but this is different from arriving after-hours and being simply prevented from accessing your airplane. That would seem to run afoul of rules about private property, esp. since the tie-down is freely accessible if you fly in.
Generally, as a pilot I have always understood that I have the right to access any public airport for normal flight activities, baring some kind of NOTAM or other abnormal situation.
Are GA airports typically accessible 24/7? somewhat touches upon this subject, but it isn't well documented that these are &quot;private (or state-owned) businesses&quot;. Indeed, airplanes and public airports are regulated by the FAA, and as such probably fall under all kinds of interstate commerce laws.
As per my answer here the FAA does define &quot;Public Airport&quot; but does not specify that ground access must always be available. The answer mentioned in the question, you link here covers the general scenarios where issues could crop up:

Private Airports: Are generally free to make rules as they see fit and could potentially prevent you from entering the property even if the tie down they offer is free. There are lots private airports in the US and there are even some big airports that are privately owned. Private airports while conforming to certain federal aviation regulations may ultimately be built on private land which falls under different (often local) regulations.
Ports Of Entry: An airport that has customs facilities may prevent you from accessing your aircraft prior to clearing customs or if they have another reason not to let you onto the ramp. This can get tricky as its often administered by the TSA.
Local Regulations: Airports are often owned by local governments or port authorities there is nothing preventing them (as far as i know) from making a rule/regulation that prevented field access at certain times.

The most frustrating issue in my experience is the &quot;Private FBO&quot; problem. Often times airports are publicly owned but physical ramp access is handled by Private FBO's that may chose to not be open 24/7 or may (what sounds like in your case) station a clueless guard at the gate after hours. This creates more of a practical issue than a regulatory one, either the owning authority needs to mandate the FBO allow people onto the ramp at all hours or the FBO needs to step up their game a bit when it comes to educating their employees.
I'd say 8/10 times the gate code is the CTAF frequency...