This is not an area where I have any direct experience so I am just speculating here and could easily be wrong:
When access permissions are set on FileMaker Tables, they have to be set in the actual file in which they are defined. If you are working with a table that is remotely sourced from another file, you can't set permissions specific to that table in your current file, you have to open up the source file for the table to set the permissions there.
Thus, I am speculating that you may need to go the source, the SQL system from which your are accessing your data and set permissions there to make the data read only.
This assumes an ESS connection and not a case where you are importing your ODBC data into a regular Filemaker table.
Thank you for the reply. However we already have explicit rights in SQL to allow/deny write rights in SQL. That did not work...
We then change the permissions within Filemaker to prevent writes in SQL but that does not work either.