On an anomaly in an impossibility in 1973, Doctor Who fans learned the First Law of Time: You cannot cross your own timeline.
Unless of course it is a 10th anniversary special. Then reverse the polarity of the neutron flow and go big.
The Three Doctors was the anniversary story arc of Doctor Who that united the first three Doctors on an adventure to save the universe from a rogue Time Lord named Omega.
The Time Lords, self-appointed guardians of time, were under an attack that was draining their power used for time travel (there was an OPEC Embargo in 1973, which probably inspired the writers for the Time Lord “energy crisis”). Given the severity of the threat, they made the decision to enable the three Doctors from different timelines to work together.
This probably was designed to avoid the risk of creating a paradox that could destroy all of reality.
However, when pressed on the First Rule of Time, one Time Lord on Gallifrey stated, “The First Law of Time will be observed… later.”
No phrase better describes what a society is willing to do in a hegemonic war with everything on the line. The Time Lord easily could have been “The Constitution will be observed…later.”
One only needs to look at the US Civil War to see President Lincoln suspended the right of habeas corpus as the fires of secession spread across the Maryland as one example of breaking the law out of the necessity to save the United States. President Lincoln could not afford for Maryland also to join the Confederacy, leaving Washington, DC an island in hostile waters.
If there is a serious threat, countries are willing to violate their own laws (or well established principles) to save themselves from extinction.
The same could be said for Gallifrey and the Time Lords. When their existence was threaten with a de facto state of war, stepping outside of the law was a better alternative than being destroyed.
In the event of a trial of a Time Lord who ordered the First Law of Time violated, the best defense would be a necessity/self-defense arguement, focusing on the fact the violation that they ordered was necessary to avoid greater harm caused by the attack.
Dueling Dual Doctors
Additionally, fans all enjoyed a good chuckle when the First Doctor addressed the Second and Third Doctors as, “So you are my replacements: A dandy and a clown.”
Time & War
The villain Omega had qualities similar to Khan Noonien Singh, because Omega was Hell-bent on revenge on the Time Lords for spending several thousand years trapped in a black hole (just as Khan wanted revenge for his exile and death of his wife on City Alpha Five against James T. Kirk).
Omega liked to scream and seemed a second away from a total nervous breakdown. Omega also had charming statements like, “Absolute power is absolute freedom” and that he [Omega] “should have been a god.”
Omega’s attack on Gallifrey created a de facto state of war with the Time Lords. Given the fact Gallifrey was a sovereign planet with a unified government, they were entitled to defend themselves. Countries on Earth have the right to self-defense recognized under the Charter of the United Nations, Chapter VII, Article 51. Additionally, while there are recognized rules on war, time travel is something not addressed in the Geneva Convention. Moreover, there is no known prohibition of using a recorder as a WMD.
In the end, the Doctors defeated Omega and the violation of the First Law of Time was justified for the greater good. And…the First Law of Time would be broken again in The Five Doctors for the 20th Doctor Who Anniversary, The Two Doctors and Time Crash (and arguably The Trial of a Time Lord).
We should expect the law violated again for the 50th Anniversary of Doctor Who in 2013. Who knows…we might learn how the 8th Doctor used The Moment to end the Time War.