The National Security Agency program that swept up details on billions of Americans' phone calls was illegal and possibly unconstitutional, a federal appeals court ruled Wednesday.

However, the unanimous three-judge panel of the 9th Circuit Court of Appeals said the role the so-called telephone metadata program played in a criminal terror-fundraising case against four Somali immigrants was so minor that it did not undermine their convictions.

The long-awaited decision is a victory for prosecutors, but some language in the court's opinion could be viewed as a rebuke of sorts to officials who defended the snooping by pointing to the case involving Basaaly Moalin and three other men found guilty by a San Diego jury in 2013 on charges of fundraising for Al-Shabaab.

Judge Marsha Berzon's opinion, which contains a half-dozen references to the role of former NSA contractor and whistleblower Edward Snowden in disclosing the NSA metadata program, concludes that the "bulk collection" of such data violated the Foreign Intelligence Surveillance Act.