how to restrict one user to delete record..

Handler Class
public class CannotDeleteAccount {
    public static void NoDeleteAccount (List<Account> accounts){
        system.debug('before delete trigger');
        String Userid = UserInfo.getUserId();
        System.debug('Current User id'+Userid);
        set<string> strkey = new set<string>(Label.UserGroup.split(','));
        System.debug('strkey'+strkey);
        for (Account acc: accounts){
            If(strkey.contains(Userid)){
                acc.addError('You cannot delete the Account');
            }
        }
    }
}

Call the Method From trigger 
Trigger accountTrigger on Account (before delete) {
    if(Trigger.isBefore){
        System.debug('Inside the Trigger');
        CannotDeleteAccount.NoDeleteAccount(Trigger.Old);
    }
}