What you are raising here are the underlying Constitutional issues that are just beneath the surface of this decree.  I think that if in fact you had an issue with the "union activity" and it went against your rights under the Constitution that you would have a valid gripe and a valid claim that your rights were being infringed upon.  Interesting.  Now, it does not specifically state that you HAD to o to a particular event and even gives you an out of finding a stand in or re-scheduling. The fine would be an issue as well if assessed because the event that was randomly chosen for you to attend cause this conflict for you.  Cross that bridge when you come to it or discus it with a Con Law attorney.  Good luck.