Illegal. It is illegal to maliciously resell mobile phones without authorization. First of all, a mobile phone is a high-tech product protected by patents, and its intellectual property rights are protected by law. Without authorization from the manufacturer or distributor, reselling mobile phones may infringe intellectual property rights and is illegal. Secondly, if you buy a mobile phone from illegal channels or from individuals with unclear passports and then resell it, you may be involved in economic crimes such as smuggling and tax evasion. In addition, it is also illegal to forge invoices and fabricate transaction evidence when reselling mobile phones.