WASHINGTON — The Supreme Court seemed ready on Tuesday to interpret a federal law protecting whistle-blowers narrowly, barring many retaliation suits from people who say they were fired for reporting wrongdoing. The plain words of the law, part of the Dodd-Frank Act, required that conclusion, justices across the ideological spectrum said.

“How much clearer could Congress have been?” Justice Neil M. Gorsuch asked.

The question for the justices was who qualified as a whistle-blower entitled to protection from retaliation. Most of the justices seemed ready to rely on the definition in the law itself, which defines “whistle-blower” to mean “an individual who provides information relating to a violation of the securities laws” to the Securities and Exchange Commission.

The definition seemed to exclude people who merely reported wrongdoing to their employers, and some justices said that could have been a drafting oversight.

“It’s odd,” Justice Elena Kagan said of the statute’s structure and language. “It’s peculiar. It’s probably not what Congress meant. But what makes it the kind of thing where we can just say we’re going to ignore it?”