When some of the nation’s biggest law firms agreed to deals with President Trump, the terms appeared straightforward: In return for escaping the full force of his retribution campaign, the firms would do some free legal work on behalf of largely uncontroversial causes like helping veterans.

Mr. Trump, it turns out, has a far more expansive view of what those firms can be called on to do.

Over the last week, he has suggested that the firms will be drafted into helping him negotiate trade deals.

He has mused about having them help with his goal of reviving the coal industry.

And he has hinted that he sees the promises of nearly $1 billion in pro bono legal services that he has extracted from the elite law firms — including Paul, Weiss, Rifkind, Wharton & Garrison; Skadden Arps Slate Meagher & Flom; and Willkie Farr & Gallagher — as a legal war chest to be used as he wishes.

“Have you noticed that lots of law firms have been signing up with Trump: $100 million, another $100 million for damages that they’ve done,” Mr. Trump said at an event last week with coal miners, without specifying what he meant by damages.

None of the firms have acknowledged any wrongdoing. They were targeted with punitive executive orders or implicit threats for representing or aiding Mr. Trump’s political foes or employing people he sees as having used the legal system to come after him.

The deals have been widely criticized, as they are seen by many in the legal community as unconstitutional and undemocratic. Four firms whom Mr. Trump leveled executive orders against have fought them in court, all quickly receiving rulings from federal judges who temporarily halted them.