David,
If a magnet will stick to it, I’m sure he CAN weld it.
Now, is he “qualified” to weld it?
And, to which standard?
You have been spinning your wheels for two days …
The bottom line is your question can only be answered by the Engineer of Record.
If the engineer approves it, you’re good to go!
Get a “Request For Information” or “Engineering Change Order” in writing to cover it. (RFI or ECO.)
As it stands now, AWS = American Welding Society.
Unfortunately, European steels do not carry over too well… At least not yet!
Perhaps in the 2015 edition this may change!
“An approved ANSI/EN/ISO standard”.
Who knows?
Stranger things have happened!
Cheers,
jb