In Starpires, it was important to make sure that more powerful players could not just beat up much smaller players. Nobody likes bullies especially when you are the weaker player that doesn’t stand a chance of defending yourself.
To help combat this there are penalties and sanctions for unprovoked attacks against smaller empires. The cutoff for penalties is currently set to an empire that has less than 50% of the number of planets and net worth than you.
These penalties imposed by both your own population and the galactic council get increasingly harsh the more an empire bullies smaller players
Population Upset - Your population may become upset after an unprovoked attack on a smaller empire, leading to your civilian mood being lowered.
Economic Sanctions - After repeated attacks the galactic council may impose economic sanctions on your empire which you have to pay at the beginning of each turn. These sanctions will last several turns.
Military Action - The galactic council maybe forced to take “peacekeeping” actions, launching a series of devastating missile strikes against your
Attacks are considered unprovoked if the opposing empire has not attacked you within 40 turns. A good way of checking this is by looking at your enemies list, or seeing if your relationship to the empire is “At War” under the diplomacy menu.
There is also a small icon next to an empires name in the attack menu, if attacking them may result in sanctions.