In an informational sort of purview. You can be compelled via subpoena, you can plead the 5th and things of that nature, but this is not a RICO case, the Clinton's don't have a 'right' legally to say they won't show up until the Epstein files are released, that would be not be considered an acceptable reason to defy the subpoena.
Also, IIRC B&C did raise the matter of the (lack of the full) release of the Epstein docs, but that is effectively just words. And witnesses don't have a right to "know all the evidence". If congress were trying to accuse them criminally, that would be different (they'd have rights to the prosecutions case/evidence) but they're just witnesses.
What they actually tried to avoid testifying was argue the subpoena is defective/not justified because they already answered the Committees questions for them in writing.
From the BBC:
In response, the committee voted to hold them in contempt of Congress; the full House will now decide whether to adopt that and refer it to DOJ, which then chooses whether to prosecute contempt (a misdemeanor with potential fines and up to a year in jail, though historically prosecutions are rare)
And just so you know, they're part of a group that's being called to testify. Its funny the commonality amongst the people who are being compelled here.
AI list, full disclosure:
Bill Clinton *Central foil in GOP/Epstein narrative; Trump has attacked him over Epstein ties and impeachment era.
Hillary Clinton *Long‑standing Trump nemesis; lock her up rallies, 2016 opponent, constant target.
Eric Holder *Frequent Trump critic; Trump and allies paint him as Obamas weaponized AG.
Loretta Lynch *Tied to tarmac meeting/Clinton email saga; conservative media staple as symbol of politicized DOJ.
James Comey *Fired by Trump; Trump calls him a dirty cop, leaker, liar over Russia probe.
Robert Mueller *Led special counsel investigation; Trump relentlessly attacked him and the probe as a witch hunt.
Merrick Garland *Overseer of Trump‑related prosecutions; Trump and allies cast him as the face of Biden DOJ persecution.
William Barr *Former ally turned critic; Barr has publicly said Trump is unfit and likely broke the law, which enrages Trump.
Jeff Sessions *First AG; Trump publicly humiliated him over recusal, still derides him as weak and disloyal.
Alberto Gonzales *Republican who has said justice should prevail in Trump cases and endorsed Harris over Trump