Ping
The other problem with the writ of mandamus (or any other legal action to compel the Senate ethics commission to act) is that the Federal Courts have historically refused to exercise jurisdiction over political questions -- that is, questions concerning the rules and regulations of coordinate branches of government.
As I'm typing this post, I thought of a third way to enforce the statute, which might work only if the statue imposes criminal penalties for non-compliance: A Federal grnd jury indictment. Although justice department lawyers would never present something like this to a grand jury, most people don't realize that a sitting grand jury generally has the inherent power to investigate any federal crime within its jurisdiction. The obvious problem is getting the grand jury to act.