Description of problem:
man auditctl:
...
       -a list,action
              Append  rule  to  the  end  of list with action. Please note the
              comma separating the two values.
...

man audit.rules:
...
       -a action,list -S syscall -F field=value -k keyname

       The  -a  option tells the kernel’s rule matching engine that we want to
       append a rule and the end of the rule list.
...

Additionally both options do work:
# auditctl -a entry,always -F arch=b32 -S execve -F euid=0
# auditctl -a always,entry -F arch=b32 -S execve -F uid=0 
# auditctl -l
LIST_RULES: entry,always arch=1073741827 (0x40000003) euid=0 syscall=execve
LIST_RULES: entry,always arch=1073741827 (0x40000003) uid=0 syscall=execve

This seems to have been fixed upstream:
https://fedorahosted.org/audit/changeset/418
And this fix is due to be included in RHEL6.1

Version-Release number of selected component (if applicable):
audit-1.7.17-3.el5

How reproducible:
always

Steps to Reproduce:
1. man auditctl
2. man audit.rules