Standard of review: de novo vs. arbitrary and capricious
Whether a court decides your case fresh, or only checks whether the plan was reasonable, depends on one clause in your plan document.
In Firestone Tire & Rubber Co. v. Bruch the U.S. Supreme Court held that "a denial of benefits challenged under" the ERISA civil-enforcement provision "is to be reviewed under a de novo standard unless the benefit plan gives the administrator or fiduciary discretionary authority to determine eligibility for benefits or to construe the terms of the plan."
In plain terms: if your plan document does not give the administrator that discretionary authority, a court reviewing your denial decides the claim fresh, with no deference to the insurer's conclusion. If the plan document does grant it, in what is commonly called a "discretionary clause," a court instead asks only whether the administrator's decision was reasonable, a standard often called "arbitrary and capricious" review, which is much harder for a claimant to win under.
One thing "fresh" does not mean. De novo describes how much weight the court gives the plan's conclusion, not what the court is allowed to look at. Many courts limit their review to the administrative record that was in front of the plan when it decided the appeal, and that limit is not lifted just because review is de novo, so a court deciding your claim fresh may well be deciding it on the same file the insurer had. Whether anything can be added later is disputed and cannot be relied on. That is why the internal appeal, and not a later lawsuit, is where evidence has to go in.
Why you cannot guess which one applies to you
This turns entirely on specific language in your plan document, usually buried in the sections describing the administrator's powers or the claims procedure, not on anything in your denial letter. See what is a discretionary clause for what to look for, and why the Department of Labor's own rulemaking record treats discretionary clauses as a live, contested issue in disability claims specifically.
A note on the version of this sentence you will see quoted elsewhere
This holding is very widely quoted in a slightly different form, one that includes the word "expressly": "must be reviewed under a de novo standard unless the benefit plan expressly gives the plan administrator or fiduciary discretionary authority." That version comes from the syllabus, the headnote prepared by the Reporter of Decisions that sits above the opinion on the same page. It is not the Court's own sentence, and the Court's own sentence does not contain the word.
The difference is worth knowing because it is easy to read "expressly" as a rule that a plan must use particular words to get deference. This site has not sourced how courts treat that question, so it does not tell you either way. What you can do is look at whether your plan document gives the administrator discretionary authority to decide eligibility or interpret the plan, rather than hunting for a magic phrase.
Sources
Firestone Tire & Rubber Co. v. Bruch, 489 U.S. 101 (1989), the Court's opinion text. Checked 2026-09-16.