Disabiling SMB1 on Mac OS
You can't really disable the SMB1 client protocol because SMB2 is backward compatible with SMB1.  What you can do, however, is specify that the SMB client only negotiate via SMB 2.x.

To disable SMB1 create an /etc/nsmb.conf (global settings) and/or ~/Library/Preferences/nsmb.conf (user local settings) with the following:

# Configuration file for foo.bar
  [default]
  smb_neg=smb2_only


If you set this in the global location (/etc/nsmb.conf) you will need Admin privileges to modify.  If your Macs are "locked down," meaning users don't have Admin privileges, this essentially locks out the user from enabling SMB1 and effectively disabling the SMB1 protocol.  

Secondly, what you should do is at a server level disable SMB1 by default.  This way, when any client attempts to connect, the Mac client will automatically switch from SMB1 to SMB2/3 as needed.  If it's not enabled on the server the client won't matter.