I'll take a shot....
If SNL seeks to influence the upcoming election, their 'commentary' could be construed as an in-kind contribution.
Ref....
Making in-kind contributions to candidates - FEC.gov
This law has been used against political commentators before.
Obama attempted to ban political books based on who funded the book.
The real culprit here is McCain-Feingold, which established the principle that the government could suppress speech based on extrinsic conditions such as how it was paid for. The First Amendment says Congress will make no law “abridging the freedom of speech, or of the press.” There is no proviso in the First Amendment saying that Congress can abridge freedom of speech in a manner that is not content-based. McCain-Feingold created that proviso, and the Supreme Court accepted it in the 5-4 McConnell v. FEC decision.
Obama Administration argues for book banning power
Didn't work, but I suppose it provides an avenue for a legal argument to ban political speech as a provision of campaign finance reform.
So it's not that Trump has the power, anyone has the power to use this as a legal argument to ban certain political speech.