You want to deny to user1 and user2 users to access files via ftp.

Do the following steps as:

1.vi /etc/vsftpd.ftpusers

user1

user2

2.service vsftpd start| restart

Using /etc/vsftpd.ftpusers file we can deny to certain users to access files via ftp. As well as there is another file named /etc/vsftpd.user_list can be used to allow or to deny to users.