It is customary in the U.S. high-tech industry to ask employees to give two weeks notice when they resign, and it is also usual to pay them two weeks salary when firing them. Keeping an employee in the company after firing him/her is obviously not recommended. It's often better to ask him/her to leave the offices immediately and pay the two weeks salary. It is worth noting that this two weeks notice is not a legal obligation, except if specified on the employment contract. However, it is recommended for preservation of your company's image to respect this American "custom."

If the employee resigns, it is recommended to ask the employee to work during his notice period, in order to facilitate the transition, just as in a European context. However, even if you have an employment contract with a notice period, an employee can leave at any time and you won't necessarily have any legal means to prevent him from doing so. He/she tells you that he/she is leaving...and 10 minutes later he/she is gone. Most employees will work the two customary weeks because they want to keep a good relationship with you for future references.

In theory, you can define a notice period for the time period you choose in an employment contract. This clause can apply to both parties or only to one. But in such a fast-paced job market, you will have difficulty finding employees who will sign a contract with non-standard clauses. And even though an employee agreed to sign a contract with a three-month notice period, nothing will prevent him/her from leaving the following day. Of course, you will be able to sue him/her, but if you intend to do so, you'd better be prepared to prove that your employee caused serious financial trouble to your company by leaving without notice. If you can prove it, you will win your lawsuit (assuming you don't give up meanwhile), but this will cost you a lot in legal fees and you won't get significant compensation. More likely, your attorney will recommend you not to proceed.

Just as a lock only keeps HONEST people honest, a notice clause will only prevent employees with a conscience from leaving abruptly, not the unscrupulous ones. Don't expect to be able to enforce the clause if someone decides to ignore it.