prohibitive

Tending to prohibit, preclude, or disallow.

Some countries are more prohibitive than others when it comes to hot topics like euthanasia and cloning.

Requiring an unreasonable or impractical effort.

Costly to the extreme; beyond budget.

I'd like to visit Europe someday, but the cost is prohibitive right now.

The economics of rebuilding all the stations covered by the electrification would be prohibitive, but to help bring home to the Glasgow public that their North Clyde suburban service has been transformed, not merely re-equipped with new trains, stations have at least been associated psychologically with the rolling stock by a common colour scheme.

Being the presumptive or likely winner of a contest.

“I think there’s no question about that. I think he’s the prohibitive favorite if he gets in,” Dennis Lennox, a Michigan-based Republican political consultant, told Politico.

[B]ut the math says Joe is our prohibitive nominee, we need to bring the party together[.]

A negative imperative.