How does my uncle get his citizenship papers back after he got out of prison?

Well, my unlce served 10 years in prison, after he finished off his time they took his Citizenship papers away from him. Since he does not know much about legal stuff or read that well as to understand a legal contract, he signed a contract giving off his Citizenship for life at the INS dept! They deported him and they told him that if they ever find him here they were going to fine him with 5 more years in prison. Another question is why would they do that toa Citizen??? HELP…I need a lawyer.