Strengthen

Signed-off-by: William Woodruff <william@yossarian.net>

Author: woodruffw

source/specifications/source-distribution-format.rst

@@ -75,11 +75,11 @@ No other content of a sdist is required or defined. Build systems can store
 whatever information they need in the sdist to build the project.
 
 The tarball MUST use the modern POSIX.1-2001 pax tar format, which specifies
-UTF-8 based file names. In particular, source distribution files must be readable
+UTF-8 based file names. In particular, source distribution files MUST be readable
 using the standard library tarfile module with the open flag 'r:gz'.
 
 Source distributions MUST NOT use non-pax features, even if those features are
-structurally compatible with the pax standard. Installers and other consumers MAY
+structurally compatible with the pax standard. Installers and other consumers SHOULD
 reject source distributions that are not strictly pax-conforming.
 
 Examples of non-pax features include GNU-style or legacy ("V7")-style tar members