AIP ENR 1.1 20.1. The pilot in command must plan and conduct a flight in accordance with the route specifications and applicable flight planning requirements published in GEN 3.2 and ERSA GEN when:
a. proposing to operate under the IFR on any route segments, or
b. proposing flight in controlled airspace, unless otherwise authorized by ATC.
20.4 Where no route specification has been published in the relevant en route chart, a route determined by the pilot in command, and, if in controlled airspace, approved by ATC, will be planned.
An example - YWKB DCT YPOD – All OCTA. Your GPS means you comply with GEN 3.2, there is no published route. There is a published route via HSM & HML, but this is irrelevant. Fill your boots.
Any affect? If you are buzzing along OCTA below a published LSALT you are more likely to be quizzed by even a busy ATC. In the days of Flight Service this would have vastly increased the workload of processing your flight, as you are ‘off the rails’. No real affect now. Requirements of position reporting must still be met by you.
Another example – YMEN DCT YPPF – 8,000 FT, partially in CTA. As above, but the route must be authorized (before you put the FPL in) by ATC. They will say, “NO”. (In other cases, particularly if it doesn’t affect areas close to the big airports they may say, “yes”).
ERSA GEN says depart EN by a variety of ways, but only defined to the first waypoint outside CTA, you pick DCT EN ML H345 NEVIS. After departures has finished organizing you with his other traffic you will get DCT NEVIS maybe without going anywhere nearer to ML than when you were parked at EN.
ERSA GEN says arrive PF from the SE via H345, but this only means for the bit in CTA. You can plan DRINA H345 AD PF DCT, then try your luck for direct with the clearance.
As above, your call what happens in between NEVIS & DRINA, DCT if you want.
So, either EN ML H345 AD PF, or EN ML H345 NEVIS DRINA H345 AD PF for more typing and less flying.
This is how I understand it. If I’m wrong I’d like to hear about it.