haha,good question! 卫兵 means the the army is the guard of our country ,and also could refer to the guardsman of the army base. 神圣不可侵犯 means because they are protect our country, safety and lifes,they are honorable and should be respected.Thus we should not offend them. 神圣 means they are honorable. 不可侵犯 means could not offend them. We respect soldiers although we hate war.We also have other sentences describe the relationship between the common and army.we say the soldiers are "最可爱的人" and all the soldiers have one purpose"为人民服务".these means the army serve people, and people love them.Hope it's useful.Thank you for reading it. :~）

Keep away from the guardsman

神聖不可侵犯 implies religious doctrine, the common concept is about God or ancient rulers with a God-given right. I think they are trying to warn the people to keep away from the base, and it's not proper to describe the army as 神聖不可侵犯, 不可侵犯 would be ok. Or, is it an army of God?

I can tell one one thing: that is not the way to say "no entry." No entry would be along the lines of 严禁进入.