Can you , yes. Harboring a fugitive is a felony. In other words, knowingly aiding a wanted person is a crime. It is not typical, though, to be prosecuted for that offense, at least in my experience. It can be a tough crime to prove. However, if this person is wanted for a serious crime, your certainly at a higher risk of getting arrested/charged.
If you want to help this person, he/she should be advised to deal with the warrant. Its not going to go away. Seek the advise of a criminal attorney who practices in the jurisdiction that issued the warrant.