For a FAR.25 certified aircraft, paragraphs 25.147 (Directional and lateral control) and 25.177 (Static lateral-directional stability) together effectively require that the aircraft be safe and controllable (as defined in the details of the paras) up to full rudder angle or high pedal forces, whichever is encountered first.
Therefore, aerodynamically, any FAR25 certified aircraft can be sideslipped to the maximum rudder capability throughout the flight envelope. (JAR 25 rules are similar, and the rules haven't changed a huge amount, so that statement is pretty much generally applicable)
There are, howvere, other limitations of the designs which may limit the capability of the aircraft: fuel systems, for example, may not be designed for sustained lateral acceleration and lateral fuel migration and engine fuel starvation may result from a sustained sideslip.
Other assumptions used during the design may also be violated if the aircraft is routinely sideslipped - loading cases for e.g. gusts usually assume that the initial aircraft condition is trimmed wings level; a design-limiting gust acting on a sideslipping aircraft could conceivably exceed the design loads for the aircraft. And, of course, this assumes a slow and steady control application - stamping on the rudder at high speeds is never a good idea.
These requirements are met through demonstration in certification flight test.
And the DFDR will probably reveal what was going on if someone bothers to check - lateral acceleration and rudder angle are usually recorded, and will be a fairly conclusive indication of what was going on.