Is it actionable as libel?
Better ask the legal eagles, but even if so it would seem the penalty would be limited to the damage.
Libel law Consider the damage already done through birtherism, without penalty. No penalty only the prize of POOTUS. It wont be a long term problem once the so-called 1st amendment is reinterpreted by the, new and improved, GREAT SCROTUS.
If indeed it is true that TT was tapped, doesnt that show that a judge thought there was probable cause that there was a crime. Maybe he could get some expurt legal advice from the AG.
Would you want Sessions defending you in court?

Tat