Poaching With An Angle To Intellectual Property Theft

Hello!
I was just reading through some articles on the net on how come companies sue their competitors who poached their employees on intellectual property theft.
Could you help me with the law behind this? and if it is legal to do this? I was thinking of writing an essay on this topic.
Thanks!

on the net on how come companies sue their competitors who poached their employees on intellectual property theft.
Employee is not companys property.
It is not a suitcase, bag , or computer to be stolen.
Take this case, im working with X company, and Y company approaches me and gives me an offer and i join Y company,, so even if X company files any case on Y company, Y will go scot free,
bcoz ill support Y, since im their employee now, ill tell they did not poach me, i had applied to them and they selected me,
second even if Y poached me, all discussions are verbal only and nothing they gave in writeen to me, tht they will offer me more than X is paying so leave X and join me.

what i meant to say was that some companies sue their competitors on intellectual property theft when they pick up or poach employees from the company.
so wanted to know if there is any law for such cases. Like for example the software companies sue their competitors saying that they have picked up key information of their company through the people they just hired and thus it is a theft of intellectual property.
On what basis can one file a case on intellectual property theft.?
are there any prominent examples that can be cited?
Thanks!!!

when an employee resigns, "non disclosure aggrement" and "non compete clause" comes into prominence ie the cos expects the ex employee not to share proprietory information plus enter into the same LOB for a limited time (time bound is derived from the basis of useful life of patent).
but to sue somebody or a competitor, the crime has to happen or malafide intent has to be proved.
The system of checks and balances in the above case is that company rights cannot infinge on individual right of freedom to choose any profession (sec 27 ICA)
read "ISO 27001" ISO 28001 etc for more info.
surya