Radio legalities will vary with the Country issuing the actual license to operate. In the few which I know about, mode-specific licenses (air, marine and railway) are quite clear that transmitting is only for those actually engaged in the mode, with approved activities and allowances clearly spelled out. Sometimes emergency contingencies are specifically allowed and sometimes not, but
the best legal approach is to not transmit unless you are certain that it's legal. If you have alternate means of communicating, use them instead.
Still, most licensing authorities will not be overly harsh with you if there was an absolute need for the transmissions to directly save immediately imperiled life and there was no other way to communicate available to you. In the US you'll get a letter from the FCC anyway wanting you to explain yourself in writing and a verbal scolding if they deem it wasn't warranted on first offense. If after this you later disregard what the FCC said they can get very nasty with fines of $50K and up! And if your illegal transmission caused any loss or duress to someone else you can be held liable for those losses too.
Here in the US, Ham operators like myself are legally allowed to transmit on any frequency in dire emergencies but we are still bound with the "immediate peril only and no other means possible" circumstances. They won't cut Hams any slack if we screw up doing this and they make that very clear to us from the start!
In this case, I'd ask the local ATC head what they would like you to do the next time you encounter such circumstances and then verify that you could do it legally with your licensing authority. Here's to hoping you never need to do that
