Yes, it is against the law to publish someone's phone number without their permission. It can be considered harassment, especially if done maliciously – this is known as Doxing. Depending on the nature, intent, and scope of the dox, the victim may pursue legal action. It's worth noting that doxing can be legal in some circumstances. When the phone number is already publicly available or was obtained legally, for example. When doxing is deemed illegal, the offender faces a six-month prison sentence, a $500 fine, and a criminal record.