Gambit Version 4.0 beta 14
(load "~~/syntax-case")
"/usr/local/Gambit-C/syntax-case.scm"
(define-macro (foo . o) #f)
*** ERROR -- invalid syntax (foo . o)
Also, (include "macros.scm") will splice the forms in as the documents say, but only macros in that file will be available, and you'll get an error if they use any procedures defined in the same file.