Setting: Republic of the Philippines (however, international views are also welcome).
Let's consider my friend as an example, and let's refer to his former employer as "Old Company" and his new employer as "New Company". Both companies belong to the IT Industry and are into web and systems development.
My friend resigned from his job as the Recruitment Officer of Old Company because the environment is no longer healthy for him. After that, he applied to New Company and was hired on the spot.
He had to sign an agreement with the HR Officer of New Company, stating that he is not to reveal to other people that he is now working with them. He also had to brief his close friends not to disclose to other people who his new employer is, especially to those who are still connected with Old Company.
The Reason: They believe that his former employer can sue him if they find out that he is now working with another company of the same industry (IT).
Can he really be sued? Is it illegal for a Recruitment Officer to work for another company of the same industry as his former one, even if he is NOT doing anything illegal in relation to his new job (e.g. poaching or pirating employees from OLD Company)?
Aside from the Philippines, is this legal or illegal in other countries?
Please share your views on this. Thank you.
Additional Info: My friend has not signed any "non-compete agreement" whatsoever with Old Company.