sqlplus user/pass@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=hostname.network)(Port=1521))(CONNECT_DATA=(SID=remote_SID)))
Maybe, and this might be dependantdepend on the command line environment you're using, you need to quote the string, something like
sqlplus "user/pass@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=hostname.network)(Port=1521))(CONNECT_DATA=(SID=remote_SID)))"
or
sqlplus 'user/pass@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(Host=hostname.network)(Port=1521))(CONNECT_DATA=(SID=remote_SID)))'