They did that with our blessing, and no small number of weapons, for which the Saudis paid us good hard cash. The Saudi "government," whatevaTF that is, didn't exactly send them. It merely allowed them to be sent and to be bankrolled by one prince or faction, or another.
The term "plausible deniability" applies to everything coming out of Saudi ruling circles. E.G., embarrassingly enough to the Wahabbi Saudi, is the fact that much of their oil lies in eastern territory that is populated by Shiite folks. The trick: keep Iran from getting these folks overly excited, yet keep them on a very short leash. The Russkis could undercut Saudi oil prices quite easily. (Oil has an actual value of maybe $2/bbl based on cost of production in these places. The rest my friends, is pure gravy.) The Russkis, OTOH, have always sought influence in Iran.
These Arabs ain't playing checkers. More like 4-dimensional chess.
Wonder what game Obama is playing? Lol.