Why won't macOS let me write files in a directory although it is write enabled and owned by me?

I am stumped why I can't write into a directory for which I have all permissions:

>ll -d .
drwxr-xr-x+ 1739 schwarz  staff  55648 Aug  1 22:33 ./

>touch xx
touch: xx: Permission denied

All higher-level directories have the same user permissions. The directory was copied via cp -rp from a TimeMachine backup.

macOS can manage extended security information in the form of access control lists (ACLs) additional to the Unix permissions. ACLs are signaled by ls -l via the + at the end of the permissions field drwxr-xr-x+.

One can

• view the ACLs of a file or directory with ls -e, and
• remove all ACLs with chmod -N, or
• change individual entries in the ACLs with chmod -a or +a or =a#.