In my replies, I'm assuming these are questions of general ethics not tied to any particular national jurisdiction. I am also making the assumption that by pardon we mean an executive level legal instrument declaring public forgiveness of a crime previously proven in a court of law.

Quote Originally Posted by Papewaio
If someone is pardoned can a law retroactively be applied to them and they be retried for the same crime despite the pardon?
No, IMO.

Quote Originally Posted by Papewaio
Is is possible to have a pardon be pre-emptively applied to stop a retroactive law being applied to the action?
No. As noted, I would expect a pardon to be applied in reference to a previous conviction, not as an absolution for actions that may become crimes.

Quote Originally Posted by Papewaio
Are retroactive laws just?
Yes, in certain circumstances. As one who believes in universal human rights, there are some actions that are unequivocally crimes, but may not be included in a particular country's legal code. That country may develop a better and more just legal code, at which time those who may have committed aforesaid crimes should be tried, even if what they did was technically legal at the time.

To be just however, retroactive laws should be used sparingly and against the benchmarks of universal human rights. Just my opinion of course.

Quote Originally Posted by Papewaio
Are members of boy bands really entitled to call themselves musicians?
I have no knowledge of these "boy bands" of which you young people of today speak, but if you mean the lad Mozart and the Archbishop of Salzburg's employees, I should say yes.