A simple sudoers rule should not allow the user to set the cwd:
Parses OK

Entries for user root:

ALL = /bin/ls
	host  allowed
	runas allowed
	cmnd  allowed

User root is not allowed to change directory to /

Password required

Command denied

User cannot override the sudoers cwd:
Parses OK

Entries for user root:

ALL = CWD=/some/where/else /bin/ls
	host  allowed
	runas allowed
	cmnd  allowed

User root is not allowed to change directory to /

Password required

Command denied

User can set cwd if sudoers rule sets cwd to '*':
Parses OK

Entries for user root:

ALL = CWD=* /bin/ls
	host  allowed
	runas allowed
	cmnd  allowed

Password required

Command allowed

User can set cwd runcwd Defaults is '*':
Parses OK

Entries for user root:

ALL = /bin/ls
	host  allowed
	runas allowed
	cmnd  allowed

Password required

Command allowed