To what end?
Rewrites are used to change or set key/value pairs. Flags arent key/value pairs, theyre flags, meaning you either have the flag, or you dont. Think of it this way; each incoming log statment has a list of flag names associated with it, you can see if a certain flag name is in that list, but thats it.
It would help to know what youre trying to accomplish though.

-Patrick

Sent: Monday, August 09, 2010 10:29:10 PM
From: Steve Barnes <steve@echo.id.au>
To: syslog-ng@lists.balabit.hu
Subject: [syslog-ng] Using source tags in rewrites? 
Hi

Is it possible to use source tags in rewrite rules? The documentation
indicates only macros are acceptable?

Using Syslog 3.1.2.

Cheers

Steve

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