Existing employment obligations after beneficiaries depend to a large extent on state law. In general, post-approval employment allows the employer to fire the employee forever or even for no reason (as long as the reason, if any, is not expressly illegal) and allows the employee to dismiss for any reason. There is no obligation to continue working in the future. Therefore, if an employee requests a raise, there is no problem with the consideration because the employee is not legally obliged to continue working. If an employer demands a reduction in wages, there is also no contractual issue with the consideration, since the employer has no legal obligation to continue to employ the employee. However, some States require additional considerations than the prospect of continued employment in order to enforce the conditions required by the employer at a later date, in particular the non-compete obligations. Civil law systems assume that an exchange of promises or a correspondence of wills alone and not an exchange of precious rights is the right basis. So if A promises to give a book to B and B accepts the offer without giving anything in return, B would have a legal recourse on the book and A could not change his mind to give it to B as a gift. However, in common law systems, the concept of culpa in contrahendo, a form of estoppel, is increasingly used to create obligations in pre-contractual negotiations. .