Andrew Napolitano, the senior legal analyst for Fox News, has been temporarily sidelined following his unproved assertion last week that former President Barack Obama had asked for British assistance in spying on Donald J. Trump, a person briefed on the decision said on Monday.

Mr. Napolitano did not appear on Fox on Monday, even though there were two news events that normally would have called for his services: hearings involving the F.B.I. director James B. Comey, and the Supreme Court nominee Neil M. Gorsuch.

Mr. Comey’s hearing touched on Judge Napolitano’s allegation — which both President Trump and his press secretary, Sean Spicer, repeated — that British intelligence officers wiretapped Mr. Trump at Mr. Obama’s request.

It is not clear how long Mr. Napolitano will be off the air, but his absence from Fox’s airwaves on Monday was an indication that the network was not pleased with the unwanted attention focused on his unfounded allegations.