Here's how I would do it:
The first time an enemy attacks a colony--and, heaven forbid, conquers it, re-capture it--and demand an official apology and reperation payments for the purpose of rebuilding said colony.
Wouldn't object to such demands, but I don't think it's necessary, either, since they're unlikely to give either.
Refusal constitutes an act of war.
Lovely. You'll end up losing millions, if not billions, of your own citizens unnecessarily. Good luck keeping the Federation from being overrun after Starfleet is severely weakened from numerous such wars and the other powers pounce on it.
I would also include an ultimatum: If said enemy power EVER attacks the Federation again...EVER...regardless of size...Starfleet would strike back with DOUBLE the force inflicted by the enemy.
Again, lovely idea. Of course, one of the problems there is that Starfleet is not militarily omnipotent. How seriously will anyone take your words if they can see that you've weakened Starfleet again and again by committing it to wars over small systems that weren't necessary to actually secure the safety of those systems?
When I was a child, my mother taught me an important lesson: You should never make a threat you're not prepared -- or physically capable -- of carrying out. Your proposed responses might work at first, but they would quickly render the Federation incapable of carrying such threats out again in the future.