Abbott Laboratories v. Gardner
In Abbott Laboratories v. Gardner, 387 U.S. 136 (1967), the Supreme Court set out three tests that informal agency action must meet in order to be considered final agency action that is ripe for judicial review.
First, the action must involve an issue that is appropriate for judicial review, such as a purely legal question. Second, it must be a definitive statement of the agency's position and not merely a tentative view or the opinion of a subordinate official.
Finally, the party seeking review of the action must be faced with serious hardship if he is not allowed to obtain pre-enforcement review.
In Abbott Laboratories itself the third requirement was satisfied by the fact that the affected companies either had to expend substantial amounts of money to comply with the regulation or not comply and risk serious criminal and civil penalties.