21:56 Feb 5 

Sometimes these documents are like trying to unravel a ball of wool after the cat's been playing with it.

21:47 Feb 5 

Hi David
"...til enhver tid..." is related to "gældende regler"...

My suggestion would be:

You are informed that with this appointment you are subject to the rules applicable in general at any given time to officers of the reserve and to the regulations established specifically for this position.

21:20 Feb 5 

These formal declarations are always so difficult to work out for us native English speakers because the word order is so, well, foreign :). As Gitte has pointed out, some of the clunkiness may be due to misunderstanding arising out of this, but the (unnecessary?) "herewith" so close to a "with" doesn't help. Here's my effort, using Gitte's suggestion:

"You are informed that with this appointment you are at all times subject to the rules applicable to officers of the reserve in general and to the specific regulations established for this position, …" You could maybe start with "You are hereby informed ..." if you want it to sound a little more formal.

I hope Gitte will let us know if I'm particularly wide of the mark.