Usher, Scooter

Mum On Biebs

1/28/2014 1:05 PM PST BY TMZ STAFF

Usher and Scooter Braun had nothing to say as they arrived back on U.S. soil after spending time with Justin Bieber.

Several photogs peppered both -- especially Usher -- with questions about what is loosely being described as an "intervention."

Not a word from either.

Based on what we know ... Bieber's not down with either rehab or therapy.