Is this legal to track full IP addresses in the US?

Is this legal to track full IP addresses in the US? Any website seem to be private property, lot of them contain valuable items, so it’s understandable that you may want to know who visits it. What is the legal outline for that?

Do not see why not

a) normal apache webserver also checks IP addresses and logs this
b) normal system daemons also (ssh/ftp/…)
c) why would ‘your’ web service be any different ?