This change is updated in the US code title 26 section 274 and reads
"(a) Entertainment, amusement, recreation, or qualified transportation fringes
(1) In general No deduction otherwise allowable under this chapter shall be allowed for any item--
With respect to an activity which is of a type generally considered to constitute entertainment, amusement, or recreation, or"
That is it. No baseball games, movies, operas, roller derbies or golf tournaments. Golf deserves a special mention as memberships for recreational or sports clubs are also disallowed. By disallowed it means they are non-deductible. They aren't illegal, but can't be included as a business deduction on a tax return.
How far this expands is currently unknown, and will of course be defined as cases are tried. For example, if you take a client out for a few drinks at a bar, is that a meal or entertainment? Are two pints of Guinness a meal? What about two martinis? There are no answers here.
This is effective for the 2018 tax year.